Illustration from The Nao of Brown

She'd be a tooth-achingly sweet "pixie dream girl" if she didn't also suffer from sudden, invasive, compulsive thoughts of harming other people. Graphic novels excel at moving smoothly from the internal to external world, combining the action and intensity of a movie with the access to inner life of a novel. When Nao's sitting in an aeroplane, we see her vision of herself opening the emergency door. When she's confronted by a pregnant woman, she's overwhelmed by thoughts of stabbing the swollen belly. We, like Nao, are sometimes initially confused about whether she's really done these things or not.

Her meditation, therefore, and her interest in Buddhist drawing, aren't just an adorable pastime – she feels constantly on the verge of breakdown. Dillon's illustrative style is clear and crisp, but incredibly expressive; the motion of Nao's shoulders, the tilt of her head as she's talking, let us know that she may be about to have another compulsive episode.

The book is very funny about the experience of learning meditation and Buddhism – however hard we try to rise above ourselves, we're always irritatingly anchored, and the beaming faces of the slightly over-keen teachers at Nao's local meditation centre tell the reader it's OK to laugh, even while Nao is taking it all extremely seriously.

Nao's story is interspersed with the elliptical tale of Ichi character Pictor, a half-man, half-tree creature who, despite having a conker for a head, goes off to join the army. The rich, illustrative techniques of the Pictor pages, with their nods towards the decorated margins of a medieval Book of Hours, form a neat contrast to Nao's story. We can see why Nao might be drawn to these strange, serene images with their intricate detail demanding close examination.

The style contrasts, very deliberately, with the sketchy, sometimes impressionistic, illustration of Nao's own story. The narrative is meandering and thoughtful, taking in Nao's flatmate, her family and her friend and boss at the toy store. There's a light plot: Nao fails to see that her friend is in love with her, and her relationship with the washing-machine repairman is inevitably threatened by her OCD.

The end reads as Hollywood romantic comedy in a way that's unworthy of what went before. But then, as Buddhism would tell us, to focus on the destination is to look in the wrong place. The matter of life, and of a book, lies in the journey, not its end, and this novel is a very fine journey indeed.

• The Liars' Gospel by Naomi Alderman is published by Viking.