This book is a revelation. Anyone for whom the name Alastair Campbell conjures up the image of a glowering bully professionally adept at manipulating words to suit his purposes will be confounded by it. For the personality emanating from his debut novel, about a psychiatric practice, is that of a swimmy-eyed sentimentalist whose verbal and inventive powers are remarkably meagre.

Slackly put-together sentences meander through thickets of irrelevance. Grammar slips awry (“Each of the morning's patients was challenging in their own very different ways”) and tautology (“knock-on consequences”) distends prose that is painfully prolix. Robotic dialogue (“You have lost your wife, though I am not convinced that cannot be salvaged at a later date”) goes along with an unfortunate propensity for jargon even at moments of would-be intense emotion: as his domestic life implodes, the novel's hero unhappily reflects, “With his family, he got into certain habits early on, and never really changed the skills set.”

Occasionally enlivened by unintended ambiguities (“The worst thing about going to a whorehouse was the moment of entry”), Campbell's writing is for the most part unwaveringly banal. One character lives in “a nice flat provided by the local authority”; another has liked to visit “a nice flat or a nice house with a nice enough prostitute living inside”; a third takes his mistress to “a nice hotel in Ireland”. Perceptions are matchingly trite: “Like people, some papers looked more important than others.”

What makes this torpidity particularly surprising isn't just Campbell's reputation as a master of seductive spin but the fact that his novel broaches issues - drink problems, depression - whose dramatic impact on his own life he has publicised. At his book's centre is Martin Sturrock, a psychiatrist “widely viewed as one of the best ...in the business". Around him are ranged patients representing specimen case histories: a depressive, an alcoholic, a casualty of a fire, a raped Kosovan refugee, a prostitute and - by way of comic relief - a man mistakenly regarded by his wife as a sex addict.

Among these diagrammatic figures, the burns victim receives therapy documented in most detail. Instructed by Sturrock to contemplate the contents of a box of raisins, she notices “they all had a very wrinkled look”, but “every single raisin was different”, and “if every raisin can be different, so can every living thing”. Liberated by this insight (“A humble raisin had taught her a lesson that no RE or social sciences teacher had ever been able to”), she casts off her trauma.

Dried fruit isn't Sturrock's only therapeutic tool, but depiction of his other strategies stays sketchy, for the book's chief interest lies elsewhere. Clangorous ironies stress that this alleviator of depression is himself dangerously depressed. Urging patients to be open about their predicaments, he remains clenched about his own. Worse, while counselling a woman damaged by prostitution, he is, as a longtime user of prostitutes, secretly drawn to her.

After apathetically dragging its way through more than 200 dispiriting pages, the book suddenly erupts into near-manic euphoria. Miraculous-seeming recoveries of morale break out on all sides. Even a funeral resounds with exuberance. Eulogies are rapturously received. An erstwhile sufferer from catatonic depression (“possessor of one GCSE, and probably the lowest-paid person in the church”) is elated to hear “hundreds of people applauding him” as he addresses them over a coffin with “hundreds of flowers piled up on it”. Near the novel's end, a Bible opened at the Book of Job is spotlit - only too appropriately, perhaps, for any reader persevering to this point will have displayed superhuman patience.

All in the Mind by Alastair Campbell
Hutchinson £17.99 pp304

Times Recommends

• The 100 Best Books of the Decade
• The Times picks the 50 best paperbacks of 2009
• The conversation: James Ellroy