The Wren in the Holly Library by K.A. Linde

Here is a summary with spoilers of The Wren in the Holly Library

Thirteen years ago, monsters emerged from the shadows and plunged the world into chaos, igniting a war that nearly wiped out humanity. In the midst of the destruction, the Monster Treaty was created—a fragile agreement with life-threatening consequences for those who dared break it. The treaty dictated that monsters would abide by human laws, including prohibitions against murder, while humans were forbidden from interfering in monster affairs unless those actions violated human law.

Enter Kierse McKenna, a skilled thief who grew up in the war-torn, now monster-ridden New York City. Her only goal is survival—keeping herself and her chosen family, Gen and Ethen, safe. Kierse specializes in stealing high-value items for the wealthy, and when we first meet her, she’s in the middle of a job, effortlessly breaking into a home to steal a diamond ring. But just as she’s about to escape, she’s caught.

The man who stops her introduces himself as Greaves. He isn’t just any man—he’s a monster, and he claims that Kierse isn’t human. The way she infiltrated the house unnoticed proves it. He tells her that magic is very real, and despite her skepticism, she soon learns he isn’t lying. Greaves offers her a job—one that could lead to more information about Amberdash, the man who initially hired her for this job. Uncertain, Kierse decides to take a day to think it over.

Back in the city, Ethen catches up to her, shocked that she survived the encounter (since she technically broke the monster treaty) and even more surprised that she has the ring. Kierse delivers the stolen item to Amberdash but warns him that he should do more research before sending her into the homes of monsters.

Returning to her sanctuary to talk with Gen and Ethen, their conversation is cut short when they’re suddenly attacked. Druids descend on them, specifically targeting Kierse under the belief that she now works for Greaves. Desperate for safety, they flee to the only place they can think of—the Wolf Den, where Kierse’s friend, Nate, is the pack leader.

While regrouping, Nate confronts Kierse about her past, bringing up Torra, a woman who was once Kierse’s girlfriend before mysteriously disappearing. He also reveals that the druid who attacked her, Declan, works for Lorcan—a druid leader and Greaves’s sworn enemy. Nate warns Kierse that Greaves is a powerful figure, one of the original signers of the treaty, and still holds considerable political influence.

With few options left, Kierse decides to take Greaves’s offer.

She meets with him to negotiate the terms of her employment: she demands five million dollars and guaranteed safety for herself and her friends. Greaves agrees, on the condition that she will be trained in weapons, move in with him, not stay in contact with her friends (it will protect them) and keep all of his secrets. The deal is struck.

During their conversation, Greaves admits that while he doesn’t know exactly what Kierse is, he can tell that she’s immune to magic. He then reveals that he himself is a warlock. Her first mission? Steal a spear from the Third Floor on the Winter Solstice—just weeks away. The tight deadline unnerves Kierse, but the Third Floor is also the last place her missing girlfriend, Torra, was seen, making the job impossible to turn down.

Kierse begins training, both in combat and in studying magic. But Greaves is determined to learn more about her true nature. He takes her to The Covenant to meet Dr. Emmaline Mafi—his ex. Emmaline warns Kierse against taking a test to determine her species, saying it will only backfire and that she shouldn’t trust Greaves. But Kierse, trusting no one, proceeds with the test anyway.

Later, in a separate POV, Emmaline examines Kierse’s blood and texts an unknown number, stating that she may have found something. The number responds: Is he counting on you?

As Kierse’s training progresses, Greaves takes her on a test mission, having her steal an object while exposing her to magic to see how she handles it. Posing as Greaves’s “pet,” they travel to Chicago and infiltrate the home of another warlock couple, Imani and Montrell—former allies of Greaves, now enemies. Kierse plays her role well, and despite her efforts to remain detached, she begins developing feelings for Greaves, emotions that intensify when they are forced to kiss to maintain their cover.

Inside the house, Kierse successfully finds the hidden object but also stumbles upon a room where a white powder is being manufactured. Exposure to the drug affects her in a way she doesn’t understand, and just as she starts to collapse, Greaves finds her and takes her home.

Later, in Imani’s POV, she realizes Greaves stole letters from her vault—along with enough wish powder to kill quite a lot of people.

When Kierse wakes up, Greaves is visibly concerned. He admits he knew about the drugs but didn’t anticipate their effect on her, expressing guilt. But Kierse isn’t fooled—she realizes she was played. As they talk, Greaves burns the stolen letters, which she assumed contained information about the spear but turned out to be personal. Their conversation shifts to a legend about the Oak and Holly Kings, and Kierse notices eerie similarities between their lives and the myths. Coincidentally, Greaves’s sign is the Holly.

Determined to learn more, Kierse sneaks out to meet Nate but is intercepted by Declan, who invites her to meet with Lorcan. She agrees and has dinner with him. Their interaction is flirty, though Kierse plays it as a test. Lorcan reveals that he was the one who initially hired her—through Amberdash—to break into Greaves’s house and suggests they continue working together. Kierse remains noncommittal, saying she must inform Greaves. Lorcan is unbothered and gives her his number.

Back at Greaves’s house, she tells him everything. In turn, he reveals that he and Lorcan were once like brothers—until Lorcan betrayed him.

Training continues, and another warlock, Kingston, arrives. He is Greaves’s mentor and suggests Kierse might be a warlock who needs to replenish her energy. That night, Kierse and Greaves sleep together.

Shortly after, Emmaline calls. Another test is needed. This time, the results confirm that Kierse is neither human nor warlock. They speculate she may be an absorber—someone who takes in magic. But Greaves suggests she might be something much older.

In another POV, Greaves’s right-hand man, Edger, deletes Kierse’s medical records and discovers that Emmaline is working with King Louis, the vampire king. Greaves orders an investigation into whether Kierse’s blood has been shared.

To further test Kierse’s magic, Greaves takes her to the Underworld, which connects to the Third Floor. She bypasses all wards undetected. Seizing the opportunity, she hunts for Ork—the person who took Torra. Upon finding him, she learns Torra was trafficked and is now paying off a debt to the vampire king. She manages to find Torra and tell her this. She promises to save her.

Back home, they continue to work on Kierse magic. Kierse discovers that she might have a power where she can move a lot faster than others. Greaves comes up with the idea, of instead of her just walking through wards with her absorption power, maybe she can absorb the ward itself, taking it down completely. Kierse continues to work on her magic to complete that task. 

Since Kierse can move in and out of the Third Floor unnoticed, she visits Torra despite having no plan for her own escape. While there, she encounters a vampire who knows secret routes. She discreetly follows him, unintentionally securing her exit strategy for the night of the heist.

On her way home, Lorcan stops her for another conversation, which ends with the two exchanging numbers. When she finally returns, she informs Greaves about her discovery and the encounter. Excited by the new information, Greaves kisses her—only for their moment to be interrupted by a phone ringing. A burner phone. One she isn’t supposed to have.

Greaves answers. It’s Nate. Ethen and a large portion of the pack have been poisoned. Furious, Greaves orders her to go save her friend, but in doing so, she has broken their contract. He tells her not to return.

Kierse arrives to find the wolves suffering from the same wish powder she once encountered. It’s forcing them to shift uncontrollably, and it’s killing Ethen. Desperate, she taps into her magic, pulling the poison from his body—almost killing herself in the process. She passes out.

She wakes up three days later, the day before the solstice. With her friends safe, she returns to Greaves’ house. (Unbeknownst to her, we see from the cook’s POV that Greaves has been heartbroken over her absence.)

Kierse and Greaves have a deep conversation. She opens up about her past—about Josh, the man who raised and trained her, but also the man who abused her. He beat her to the brink of death and left her for dead. That was the night she found Torra and Nate. She admits she hopes Josh is dead—she put a knife in his back that night and never looked back. This, she explains, is why she struggles with trust, why she broke their treaty in the beginning. She wasn’t sure if she could trust Greaves. But now? He’s the only person she’s ever truly trusted.

They spend the night together before preparing for the solstice.

At the Third Floor, the vampire party is in full swing. Kierse infiltrates it disguised as a human sacrifice. But Greaves is there, ensuring no one touches her. The two sneak away, searching for the entrance to the spear. When they find it, the wards are layered and heavily protected. Greaves manages to break one, allowing Kierse to pass through unscathed due to her magic. However, Greaves can’t follow. Before they can find a solution, someone else is already inside. They grab Kierse. She blacks out.

When she comes to, the Vampire King has her. He feeds from her, testing what her blood can do. It dulls her senses. Even so, she spots the spear. Seeing an opening, she grabs it. The moment her hands touch it, her senses return. The weapon is a god spear. Empowered, she takes her shot—decapitating the Vampire King.

Greaves arrives moments later, proud of her. Together, they retrieve Torra and begin their escape.

As they leave, Kierse pieces something together—the stories Greaves had her read were about him. He is the Holly King. He confirms it. And she? She is his Wren.

Panic sets in. In the stories, Wren is the Holly King's downfall after the Winter Solstice.

Greaves admits it was always a gamble.

Once they’re free, Torra parts ways, eager to enjoy her newfound freedom. Meanwhile, Greaves reveals his mission: collecting the four most powerful artifacts. He already possesses the sword. Now, Kierse has the spear. They are halfway there.

Before they can celebrate, the wards drop. They rush to the library and find Ethen and Gen held hostage—by Lorcan.

Everything clicks. Lorcan is the Oak King.

He demands the spear in exchange for their lives. He turns to Greaves, threatening to kill Kierse unless he surrenders the sword. Greaves hands it over.

Lorcan wastes no time—he uses the Sword of Truth on Kierse. The magic strips away her secrets, revealing what she truly is: a wisp, the last of her kind. And more than that—she is fae.

Betrayal washes over her. Greaves knew. He knew for a long time and never told her. But he is too focused on the fight to see her breaking.

As Lorcan and Greaves battle, Kierse seizes the moment to save her friends. The sword’s magic has unblocked her own, making her stronger. The spear speaks to her. As they escape, realization dawns—if Greaves dies, she wouldn’t be able to live with it, even if she is furious at him.

She turns back.

Lorcan is winning.

She rushes in to help but is struck by a blast of god power. She crumples.

Greaves, desperate, tries to tell her how to break his magic. It’s not enough. She’s dying.

Ethen and Gen rush to her side, refusing to let her go. They clasp hands, and something shifts. Magic erupts. Ethen is a druid. Gen is a High Priestess. Together, they restore Kierse’s life.

The three of them rise.

They tell Lorcan to leave. He does—but not before promising they will see each other again. Druids and wisps are closely connected, after all.

Kierse turns to Greaves. And then she leaves with her friends.

The last chapter is a pov from Greaves. He is sad that Kierse left. But he is also angry that 1 week ago he had two powerful magic objects, and now he has none. He then gets a call, he has a lead to the third object, the cauldron. And he is going to need a thief to get it.