In 2007 Prince played a 21-night stand at the O2 in London. The author of this book went to 19 of the shows and "deeply regretted missing the two I couldn't attend". The inscrutable pop legend also delivered full-band sets at 14 of the after-show parties, and Matt Thorne saw all but one of those, too.

You wonder if it's possible to care any more deeply about a musician until the moment he's ushered into Prince's Los Angeles living room for an exclusive album launch performance. The publicist from Universal whispers, "I'd rather piss down my leg than miss a second of this", and Thorne takes a surreptitious step away from her.

Obviously you need a lot of belief to justify hammering out this length and level of scrutiny, but too much affection tends to fog the vision. You can lose sight of the key details that might engage someone outside the subject's central orbit. Someone like me, in fact: I saw the head-spinning spectacle of the Purple Rain and Sign O' the Times tours and felt weak with admiration, yet I've never felt any compulsion to read a book about Prince. He seems easy to applaud but hard to love, a dazzling technical wizard offering no real chance to connect with him.

The first half of this chronicle is highly engaging, a mass of background colour that maps out his evolution. When his parents split he's brought up by his jazz musician father, and it's the sight of John "Prince Rogers" Nelson on stage surrounded by attractive women that spurs his son into a career plan. Prince Nelson Junior is manically driven, promoting himself as a sort of "Stevie Wunderkind" prodigy. "A tiny little person with huge hair", he turns up backstage aged 16 at a Todd Rundgren show announcing, "I'm real talented and I play everything." Joni Mitchell remembers him in her audience a year later  "quite conspicuous because he's got those eyes like a puffin, those Egyptian eyes, those big exotic eyes".

His drive and creativity are a marvel to behold. He holds competitions to see who can write the most songs in a day. He hires a 60-piece orchestra only to mothball the recordings in his famous vault where "hundreds" of songs apparently await release. He collaborates with a bizarre variety of people, from Sheena Easton to Kate Bush and Miles Daviscorrect (and let the record reflect that he wrote A Couple of Miles for Davis, who returned the favour with Half Nelson), and any psychologist could find a formative link between his lack of a mother figure and the succession of band members he adopts as either muse, lover or both  Vanity, Jill Jones, Cat Glover, Wendy Melvoin and Lisa Coleman among them.

Thorne painstakingly tracks down many of these fellow travellers, though he can't prise a great deal out of them. With the subject himself unavailable to shed any first-hand light, the game begins to drift slightly from the half-time whistle, and we're offered greats slabs of live concert review to sustain our attention. Past his commercial peak, the Prince that now channels his energy into self-mythology and highly publicised spats over his "enslavement" by Warner Brothers is nowhere near as beguiling as the mythical creature bursting out of Minneapolis into a brave new world of supercharged funk-blues and rock theatre. Who gives a monkey's that "he kills off seven alternative Princes" in the straight-to-video movie 3 Chains o' Gold to symbolise his rebirth outside the manacles of a cruel and acquisitive major-label system? Even Thorne concedes that, while his hero made many of the old guard look hopelessly unfashionable in the 1980s, he himself seemed "out of synch" a decade later. One '92 outtake called Poor Little Bastard, he rather sweetly admits, is so godawful that he plays it whenever he feels his passion for the back catalogue needs a brake pedal.

This second act is slow going and could do with some deeper musical analysis. We're told Prince "hates the Beatles" and had "little first-hand knowledge of jazz" or that a song has "an overly complicated arrangement", but you yearn for some real insight into the great cauldron of influence that produced a musician so effortlessly skilled that his sets ricochet from the B-52s' Rock Lobster one minute to Wayne Shorter's Footprints the next. Thorne makes the valid point, though, that the trajectory of his career  spanning all the shifting tectonic plates of the old music business model to survive on his own terms  could never be repeated.

You get to understand Prince as a cold and calculating operator but you never feel close to the beating heart of a human being. Perhaps the latter is impossible, partly because he remains so closely guarded and partly, I suspect, because beneath this sparkling empire lurks a man with very little warmth indeed.