Already a hugely successful YA novelist, Leigh Bardugo is delivering fantasy to a new demographic. Her adult debut, “Ninth House,” is wry, uncanny, original and, above all, an engrossing, unnerving thriller. The action takes place at Yale University, where magic complicates reality. Ghosts crowd the campus, and elite clubs capitalize on the power that pervades the grounds, using it to predict the markets and peddle influence. It is up to the student delegates of the House of Lethe to keep things from going supernaturally sideways as these organizations perform the rites that build their wealth and eminence.

Galaxy “Alex” Stern is an unlikely fit for Lethe and for Yale. She has no trust fund, no prep school past; instead, she was a dropout and a drug addict. But Lethe recruits her because she can see ghosts. It’s a gift that has brought her only trouble and trauma, but it’s a talent they need. Lethe offers her an escape, even if it’s one that leaves her feeling completely out of place.

When a routine magic ritual goes wrong on the same night a girl is killed, Alex feels impelled to investigate beyond her official capacity. She identifies with the victim, a town girl whom her faculty advisers seem all too willing to ignore. Alex’s peculiar gift opens new avenues of inquiry and draws her into a tense relationship with one of the most famous ghosts of New Haven.

The world that Alex navigates feels intimately lived-in. A Yale alum, Bardugo name-checks New Haven’s buildings, streets, restaurants and stores. Except for Lethe, all the secret societies featured in the novel actually exist. These elements create a fluid feeling of not knowing precisely where reality leaves off and fantasy takes over, creating layers of mystery for the reader.

The story unfolds (and folds in on itself) in three timelines, and a reader could be forgiven for occasionally thinking, “Wait, when are we again?” The parallel trajectories create a dramatic balance of suspense and payoff, which occasionally feels convenient. During one gripping action sequence, a flashback reveals pivotal information about Alex’s past — a past we thought we already understood — just in time to help her in the present. There is a palpable sense that the narrator was holding out on the reader for effect, but the feeling of unreliability is salvaged by Alex herself, who is wily and cagey enough to withhold important details.

Alex is a potent mix of flinty strength and raw vulnerability and a brilliant instrument to channel the novel’s tone, which is simultaneously elegant and grotesque, eerie and earthbound.

Alex stands at the crossroads of privilege and pragmatism, and her unique point of view opens the most relatable and often the funniest windows into the story’s themes: “It was one thing to be told magic existed, quite another to have it literally give you the finger.”

Investigative momentum propels Alex through some convincing misdirection before she comes to a climactic confrontation that resonates emotionally. Alex gets answers, but they lead her only to new questions, leaving readers hungry as a hellbeast for the sequel that is sure to follow.

Ellen Morton is a writer in Los Angeles.

Ninth House

By Leigh Bardugo

Flatiron. 480 pp. $27.99