Sanity makes for lousy fiction: Memorable stories tend to emerge from the moments when people snap their tethers and defy expectations. But mental illness in contemporary fiction is often lousy, too. Readers endure either earnest clinical depictions — usually thinly veiled critiques of the pharmaceutical-industrial complex — or out-there prose that's supposed to evoke madness but instead reads like gassy rambling.

Adam Haslett's brilliant second novel, "Imagine Me Gone," is a remarkable exception, capturing two troubled minds with rare empathy, realism and insight. John, the family patriarch, is a depressed man who struggles to maintain his job as well as his wife and three children. (The family splits between England and the East Coast, echoing his mental fragmentation.) "There is no killing the beast," John writes. "It will hunt me until I am dead." Early on we learn he's proved right.

His son Michael's struggle is no less intense, but he is also an utterly enchanting character. The first clear glimpse of his illness comes in a series of teenage letters to his aunt written on a cruise ship. Something's off when he casually deadpans his brother's disappearance: "Alec is currently missing. We lost him at a lunch buffet." Then it's clear he's fantasizing: "Apparently, he'd been abducted by a child-prostitution ring down on Deck 3." Then his voice becomes absurd and troubling: "Turns out this puppy is a full-on white slaver!"

As in those letters, so in his life. Michael's every riff on music, feminism and racism is seductive to the reader — and, for a time, those close to him. But he ultimately alienates everyone except his family, who by default becomes a function of his increasing problems: his mother isolated, his sister and brother fearful of relationships and parenthood. His brother Alec is accomplished but restrained, living in "one of the thousands of adult dorm rooms in Manhattan, where credentialed children performed their idea of adult lives."

This struggle to reconcile home, family and mental stability culminates in a latch-ditch effort on Alec's part to sherpa Michael to some kind of normalcy. The drama is foreshadowed in the deliberately vague opening pages, in which Michael leaves a puzzling outgoing message impersonating a doctor. "You have gone on holiday with your younger brother, in the hope you might finally tear your eyes away from the scenes you have been fixedly contemplating your entire life," he intones.

A few hundred pages later, we have the maddening reasons for the "holiday," and the crushing "scenes" he's been contemplating. It's a memorable, funny and ultimately heartbreaking trip.

Mark Athitakis is a reviewer in Phoenix.