Fame and its irrational force is a riveting subject for modern Britain, and Alastair Campbell can claim more experience of this than most, having basked in the reflected glory of the best-known British politician in a generation. Anyone who has had the misfortune to suffer a friend becoming famous will know the feeling of being at once elevated by the acquaintance, yet relegated to the shadows by the vast selfishness that fame makes possible. That is the awkward but enticing position of Steve, the highly unreliable narrator of Campbell's second novel.

The addictive quality of celebrity is at the centre of what might loosely be called a thriller. The Maya of the title is a wildly successful actress, devoid of the steel and drive that this breed usually possesses in spades. Little more than a commodity, she is devoured by all around her, but remains mystifyingly bland: early Diana meets Keira Knightley.

Steve is the obsessed old friend of this saintly creature. Maya has a truly horrid TV presenter boyfriend called Dan, who resents Steve. And Steve's missus, Vanessa, is a long-suffering, rather maudlin presence who goes along with her husband's fixation on the actress to the point of witlessness. Fortunately, there is skulduggery afoot at the hands of showbiz agents, the wicked media and enterprising gumshoes.

The scandal surrounding the News of the World's royal editor Clive Goodman must have been on the author's mind as he typed away. The feeding frenzy that surrounds the mega-famous seems to appal and excite Campbell in equal measure.

So far, so enticing. So, more's the pity that the novel is undermined by too much clunky exposition. This, for example: "Trying not to think too much about what she had just said, I locked up the house, threw my briefcase into the car, scraped the ice off the windscreen and drove as fast as I could through the streets of Hammersmith, only remembering when I got to the Hogarth roundabout that . . ." We are dealing with a first-person storyteller here, yes, but even unreliable narrators shouldn't be so deadly boring. And I searched in vain for a memorable phrase, but it was like looking for WMDs in Iraq. We observe "the over-the-topness of the catering" at a dinner, and at one point someone describes the star character as being "double-parked in a no-comment slot".

Random thoughts are chucked in along the way, too. "There is part of me that expects Sunday traffic to be lighter than during the week but it never is." Weird, that - and of no relevance whatsoever. Halfway through the book, I was in despair. Then it suddenly improved when the twists and turns of the plot got going, helping it to chug along towards an ingenious denouement.

The most readable parts by far are those that mimic the mores and tone of the tabloids and the celeb-snooping industry that serves them so assiduously. The descriptions of sex alternate between football-manager demotic - the characters have conversations "between fucks" - and unlikely homage to Barbara Cartland: "Hours of pleasure . . . the union for which my whole life had been a preparation."

Female psychology is not a speciality. The women are mere hovering presences, tending their pregnancies and keeping their hair shiny. When very annoyed, they throw their slingbacks at the door. Campbell understands nasty men better, and the tone of office conversations - terse, faux-matey exchanges that conceal an underlying anxiety - is just right. But the whole thing groans under the presence of so many stock characters that you begin to dread the next one popping up. Maya's salt-of-the-earth, Mirror-reading dad, for example, is a parody of New Labour's head-patting approach to its old base. Bono and Bob Geldof make superfluous appearances - just in case we've failed to get the message that the modern world is obsessed with fame at the highest levels. I held my breath for a Tony Blair cameo, but sadly came there none. Maybe his rates were too high.

There's one obvious omission from this writing: any fun. A quick, raucous and pointed wit was one of Campbell's more attractive characteristics in his Downing Street years. It doesn't make it into the pages here, although his subject matter is rich in comic potential. He does, however, thoroughly grasp the manic obsessive's attention to detail, his skewed perceptions and warped sense of mission. Make what you will of that.

Anne McElvoy is political columnist of the Evening Standard and presents "Night Waves" weekly on BBC Radio 3.

Alastair Campbell
Hutchinson, 416pp, £18.99

This article first appeared in the 15 February 2010 issue of the New Statesman, Everything you know about Islam is wrong