Kate O’Hearn books in order

Come to Herm now, or you'll die, the strange voice warns.

On the magical, mist-shrouded island of Herm, Lori discovers the secret of her true nature and joins the fight for the survival of a rare species of whales. Her arrival on Herm is only the beginning of a terrifying ordeal that will change her life forever.

Mermaids, sharks, the revelation of a long-forgotten murder, a battle with a ruthless gun-trader - this unique and magical tale has the spirit of adventure and excitement Kate O'Hearn's readers found in her 'Shadow of the Dragon' and 'Pegasus' titles, along with the romance of myth and the mysteries of the widest, deepest oceans.

The spellbinding story of two cousins whose summer vacation gets swept away by a storm that lands them on the lost island of Atlantis.

The last way that Riley Evans wanted to spend spring break was studying whales on the family sailboat in the middle of the Bermuda Triangle. With only her dad, aunt, and annoying cousin Alfie for company, she is so bored staring at the waves that she’s starting to see mermaids between them. But when their boat is capsized during a sudden storm, Riley finds more excitement than she bargained for as she and Alfie are washed ashore with neither of their parents in sight. Where they’ve been shipwrecked is no deserted island, though.

Atlantis is a place beyond imagination, inhabited by both people and incredible creatures ranging from unicorns and gargoyles to talking animals. But not everyone welcomes the cousins’ arrival, and beneath the wonder of this mythical land lurk dangerous secrets—something strange is happening to the inhabitants. What Riley wants more than anything is to find her father and go home. But the closer she gets to this goal, the more the islanders seem determined to keep her from reaching it.

As Riley and Alfie unravel the mystery of Atlantis and its most terrifying part, the Forbidden Zone, they realize that the clock is ticking. If they can’t learn what happened to their parents and find a way off the island soon, it may be too late to leave.

Riley thought that her adventure was over when she arrived back home in Colorado. Although she misses her dad, she’s back with her mom and brother and has caught up with her classes at school. Though Maggie, Pea, and her aunt have to hide in their basement apartment during the day, they are making the most of things and settling into their new life.

But things get much more complicated when a gang of thieves plagues Riley’s neighborhood and her family takes in a group of children who don’t know about the Atlanteans living in the basement. To make matters worse, the Atlanteans are becoming gravely ill, and everyone starts to worry that they may not be able to survive so far from the island’s magic.

As tensions escalate, their only option is to return to Atlantis—and face all the enemies they made during their escape, plus a few new ones.

Life on Atlantis has always been unpredictable. But lately, the Community has finally started to feel like the stable home Riley hoped it could be—until the weather becomes anything but stable. After three Red Moons within a month, the latest of which brings an earthquake, it’s clear that something is wrong. But what is causing this change?

In addition to creating chaos, the storms are also damaging homes across the territories and escalating tensions between the groups. And when an encounter with the Underwater Territory goes badly, several of Riley’s friends are kidnapped! With no hope of reaching her friends on her own, Riley embarks on a quest—accompanied by Storm, Alfie, Maggie, Pea, and Kevin—to enter the Enchanted Territory and seek the Fairy Queen’s help.

But intrigue and secrets abound in Atlantis, and Riley is hopelessly unprepared for the ways that forgotten artifacts and ancient power struggles will disrupt her plans. Riley will have to learn to navigate the magical societies and finally learn the truth behind the island’s history if she is to have any chance at surviving the journey—let alone saving her friends.

A young girl. A winged horse. An Olympian war.

When Pegasus crashes onto a Manhattan roof during a terrible storm, thirteen-year-old Emily’s life changes forever. Suddenly allied with a winged horse she’d always thought was mythical, Emily is thrust into the center of a fierce battle between the Roman gods and a terrifying race of multiarmed stone warriors called the Nirads. Emily must team up with a thief named Paelen, the goddess Diana, and a mortal boy named Joel in order to return Pegasus to Olympus and rescue the gods from a certain death.

Along the way, Emily and her companions will fight monsters, run from a government agency that is prepared to dissect Pegasus, and even fly above the Manhattan skyline—all as part of a quest to save Olympus before the Olympic flame burns out.

NB: This book is also known as Pegasus and the Flame.

Emily and her winged horse face a war of Olympic proportions.

Emily, newly recognized as the Flame, is living in Jupiter’s palace on Mt. Olympus. Her friends, Joel, Paelen, and—of course—Pegasus, are there as well. The only person missing is Emily’s father, who is still being held prisoner by the CRU back in the human world. Emily wants to go find him, but Jupiter won’t allow her to leave. However, Emily does have access to a winged horse…

Determined to rescue her father, Emily and her friends make plans to sneak away from Olympus and back to New York. Then Cupid, Emily’s sort-of crush, decides to come along as well. It will be hard enough to hide a winged horse from the prying eyes of the CRU, but a winged boy as well? And when the gruesome Nirads begin a new invasion, old grudges are unearthed, new enemies are discovered, and Emily and her friends become entangled in a conflict more dangerous than they ever anticipated.

NB: This book is also known as The Fight for Olympus.

Emily and her companions, including the winged horse, Pegasus, must confront a legion of Olympic enemies.

When Emily’s father and the goddess Diana return from a visit to Earth, they bring with them disturbing news. There’s a horse called Tornado Warning that’s winning all the races, with times faster than anyone’s ever seen. What could this mean? Emily, Joel, Paelen, Pegasus, and the sphinx Alexis return to Earth to investigate—and discover a CRU plot to clone Olympians and Nirads using DNA retrieved from their previous time in the human realm.

The CRU has already created dozens of Nirad warriors, Dianas, Paelens, Cupids, and Pegasuses. Now they want to create their own Emily clone—even if the original is killed in the process. Can Emily and her friends put a stop to the CRU’s plans before Jupiter finds out and carries through on his own threat to destroy the Earth?

Emily and her winged horse, face an ancient challenge of Olympic proportions.

A deadly plague has struck Olympus. While the Olympians fade one by one, Emily’s heart breaks as she watches, particularly when Pegasus begins to slip away. Determined to save him, she embarks on an investigation that takes her back in time to the origins of Olympus and to the deadly battle between the Olympians and the Titans.

In the present, she must face the force of the CRU. In the past, she must confront Cronus, the father of the gods and leader of the Titans, who is intent on destroying his offspring. When Emily encounters the full power of the flame and a discovery that could change the face of history, will she make the right decisions? And in the race against time to save Pegasus, will Olympus find its true hero?

In order to save Olympus, Emily and her winged horse, Pegasus, venture to Hawaii—and a Hawaiian volcano—in a tale that puts a modern thrill into ancient mythology.

The ancient rivalry between the Olympians and the Titans has been rekindled. However, this time the Titans have a secret weapon—a weapon that rivals the Flame of Olympus. The balance of power is tipped in Saturn’s favor now that he has found his own Flame of Titus. Olympus is almost in his grasp! And just when the Olympians need Emily most, she finds her own grip on the flame weakening.

If Emily is going to save Olympus, she will have to save herself first. To do so, she and Pegasus must journey to the Diamond Head volcano in Hawaii to track down the one thing that can help her…but can they get there before the Titans or the CRU beat them to it?

Emily and Pegasus face their greatest challenge yet when they venture back to Earth to save a friend.

After the events in Hawaii, Emily is contending with diminished powers, a new body, and the fact that she has to teach the Titan Lorin how to use her own powers. To make matters worse, Joel has been acting strangely towards her ever since she changed, and it’s all become too much.

However, Emily has one last promise to fulfill, one she made a long time ago: to save Agent B from the secret government agency called the CRU. But when Emily, Pegasus, Joel, and Paelen arrive in London, they discover that Agent B has been captured by the CRU and the only way to free him is for Emily and Lorin to surrender.

As Emily and her friends delve deeper into the CRU’s history, horrible discoveries are made. Not only about the victims the powerful agency has been trapping and abusing for centuries, but about the very origins of the secret agency itself.

Origins that lead directly back to...Emily.

Under no circumstances are girls EVER to be allowed anywhere near dragons. THE PENALTY FOR ANY GIRL CAUGHT BREAKING THE FIRST LAW IS DEATH. Kira is twelve, and strong willed. The daughter of a retired dragon knight, she yearns for adventure and dreams of following in her father's footsteps astride her own magnificent mount. But this can never happen. 

According to the 'stupid laws' of the kingdom, she must be married by thirteen. Kira hates it, but being a girl she has no choice. Then Lord Dorcon arrives, in a whirl of destruction and fire and Kira knows the real fight is just beginning. To stand a chance of seeing her family again, and to protect the life of her younger sister, she will need every bit of willpower she can find. Let the battle commence.

One day, a young girl astride a twin-tailed dragon will destroy the monarchy and change the world for ever ...Kira and Elspeth have already broken FIRST LAW many times over. 

Now outlawed and running for their lives they are determined to stand amongst the men and fight the unjust FIRST LAW that binds the kingdom. But cruel Lord Dorcon still stands in their way and the heat of his chase is stronger than ever. Strong and determined, Kira has done all that she can to protect and shield her younger sister. But now it's time for Elspeth to grow up. 

When Paradon's muddled magic sends them travelling through time to different eras, new challenges and terrifying threats await the separated sisters. Especially to Elspeth, left all alone to navigate a past world long before the rule of King Ardon and FIRST LAW. And all the while in a strange, alien world of the future, Kira must find a way to get back to Elspeth and reunite her family once again. A prophecy to fulfil. A cruel monarchy to upend. The battle continues ...

A group of kids must stop invaders before they take over Titus—and the rest of the universe.

Fifteen years ago, Olympus was destroyed and the Olympians were resettled on Titus. Since then Earth has been declared a quarantined world. Neither Titans nor Olympians are allowed to visit and under no circumstances are humans allowed on Titus. The Titans and Olympians are keeping the peace. But the deep-seated mistrust still lingers, so when a human ends up on Titus, he could be the spark that reignites the war…

Astraea is a Titan, granddaughter of Hyperion, and now a reluctant student at the brand-new school, Arcadia. She just knows that it’s going to be awful, and that there is no way that Titans and Olympians will ever get along! At least she’s got her best friend, a winged-horse named Zephyr, to keep her company. Then the night before the first day of school, Astraea hears her parents discussing something terrifying: a human has been spotted on Titus. But that’s not possible. All routes to Earth via the Solar Stream have been closed—no one can travel between the two worlds…or can they?

When Astraea and Zephyr get detention on their first day—for fighting with a centaur—they’re sent to the orchards to harvest nectar. There they discover a human boy named Jake. How he got to Titus is a mystery even to him. But Astraea and Zephyr know they have to get Jake home before anyone else discovers him.

But what the trio uncovers is something much bigger than one misplaced human boy. It’s a scheme to take down the rulers of this world, conquer it, and then do the same across the galaxy. Can a group of kids stop the invaders? Or is Titus, like Olympus before it, doomed?

Follow Astraea, Zephyr, and their friends as they travel to a dangerous jungle world. 

Zephyr, and their team head to Nesso’s jungle world to seek help in the struggle against the Mimics.

But nothing goes to plan. The moment they arrive, they encounter a world filled with dangers they never imagined possible—from massive, hungry dinosaurs to a blisteringly hot sun. Soon Zephyr and Astraea are seriously wounded. Without ambrosia or nectar to heal them, the group realizes they are in serious trouble. But where can they go for help?

With Zephyr’s life slipping away, Jake and Tryn use their new flying skateboards to try to make it to Xanadu where they hope to find ambrosia for Zephyr and enlist help to join the fight against the Mimics.

Meanwhile, Astraea and the three centaurs must use all their cunning to keep Zephyr safe and alive. But danger comes in many forms, and it seems as though no one may be left to help them—until Jake and Tryn stumble across a lone Olympian everyone believed to be dead…

Astraea, Zephyr, Pegasus, and Tryn turn to an old enemy to save them from a desperate situation.

Jake, Nesso, and Emily have been captured by the Mimics. Their friends are determined to rescue them before it’s too late, though that’s easier said than done. Driven from their home and facing a constant stream of new attacks, Astraea, Zephyr, Pegasus, and Tryn are struggling just to survive another day against Mimics who can kill with a touch and take the shape of any friend or family member.

While Jupiter is focused on returning to Titus, Astraea knows their only hope is to take the fight to the Mimic home world and stop the Mimic queen herself. To do that, they’ll need to even the odds of seven friends versus an entire planet. So they come up with a plan to capture the one thing more terrifying than their enemy—the giant snake Lergo.

Seeking out the serpent that almost killed them seems like a terrible idea. But it will take more than one unlikely ally to save their friends—not to mention the universe—and defeat the Mimics for good.

Valkyrie: Norse Goddess. Reaper of Souls. Defender of the Weak. Not someone you want to mess with…

Freya is dreading her upcoming birthday when she’ll officially have to take up her duties as a Valkyrie. She doesn’t want to follow in the footsteps of the legends before her—legends including her mother and sisters. And she certainly doesn’t want anything to do with humans!

Freya thinks humans are cruel, hate-filled creatures, but as she observes their world, she begins to wonder what it would be like to make friends with the girls or laugh with the boys she sees. And what would it be like to live without the fear that she could cause someone’s death with a single touch?

Then when she’s sent on her first mission, she reaps the soul of a fallen soldier with unfinished business…business that sends her on an epic quest to the mortal world. Will Freya find the true meaning of being a human, or will she finally accept her destiny?

Valkyrie: Norse Goddess. Reaper of Souls. Defender of the Weak. But could she also start a war?

In the world of Asgard, living among Odin, Thor, and Loki are the Valkyries of legend. Norse goddesses, reapers of souls from human battlefields—they have the power to cause death with just one touch.

Freya is a Valkyrie—but she has not followed in the footsteps of the legends before her. She has been to the World of Man to befriend humans—and not to reap their souls.

Now she must return to the human realm on a new quest to track down the runaway Valkyrie of legend. There she will discover a dark secret that leads her to the Land of the Frost Giants where she must take on new enemies. But this time she has friends to rely on, and lots more to gain.

Freya and the Valkyries must stop a war before two worlds are destroyed.

In the world of Asgard, living among Odin, Thor, and Loki, are the Valkyries of legend. They are Norse goddesses who reap the fallen souls from human battlefields and have the power to cause death with just one touch.

At the end of The Runaway, Freya and the Valkyries were about to leave the human world when they learned that the Frost Giants, Fire Giants, and Dark Searchers had united to declare war on the Realms. Bitfrost, the legendary rainbow bridge linking the human world to Asgard, had been closed.

With their only entry back to Asgard barred, how can the Valkyries get back to fight to protect their homeland? Loki claims he knows a secret route, but can they trust him? And even if they find a way—is there anything they can do to stop the war?

As the War of the Realms spills over into Earth, Freya and the Valkyries must find a way to save not just the Norse world but the human world as well. With everything at stake, can Freya become the Hero she was destined to be?