Decoded, the first book by the New York rap mogul Jay-Z, is rather more than a memoir. This is interesting in itself, as the life of the man known to his mother as Shawn Carter is certainly colourful enough to succeed on such conventional terms.
From the shy boy in the Queens projects, scribbling in his notebook in tiny print so his peers couldn't "bite" his rhymes to superstar rapper, chief executive, entrepreneur and husband to the singer Beyoncé Knowles, this is a life with content to go around.
But as the title and cover art - one of Andy Warhol's Rorschach paintings, adapted from the visual tests used by psychologists to assess a patient's thought processes - suggest, Decoded is something that probes rather deeper.
Built for the coffee table, Decoded is packed with photographs, sleeves and illustrations, and also functions as a lyric book, bringing together three dozen of Carter's selected raps spanning his career from 1996's Reasonable Doubt to 2007's American Gangster, plus a few unreleased cuts for good measure. Rhymes are presented with numerous footnotes, drawing attention to moments of personal importance, pointing out wordplay and poetic tricks, and explaining more obscure allusions. It's meticulously detailed, and frequently enlightening in its insights into its maker's writing process.
More broadly, though, we can read Decoded as Carter's attempt to explain his own history, and, more broadly, to legitimise hip-hop as an art form. Hip-hop may be into its fourth decade and the de facto pop music of choice for a good portion of the planet, but Noel Gallagher's 2008 pronouncement that "I'm not having hip-hop at Glastonbury", prompted by Jay-Z's headline slot at the festival, suggested that it is still not fully accepted in some quarters. Even among some fans of the genre, the arrival of gangsta rap in the mid-1980s, with its tales of hustling and pimping, was deemed a corruption of block party innocence and the ghetto morality of tracks such as Grandmaster Melle Mel's anti-cocaine narrative, White Lines (Don't Do It).
It is Carter's relation of his early life as a teenage drug dealer, selling crack in the Marcy projects, that makes for Decoded's most fascinating passages. He is unflinching in the details - the addicts, "skeletal and ashy… jittery as rookie beat cops", the man who introduces him to dealing, who ends up dead in a grisly fashion - and realistic about the effect that crack cocaine had on the communities he, and others, dealt to.
But he also mounts a defence of the validity of the hustler's story. "Hip-hop had described poverty in the ghetto and painted pictures of violence and thug life, but I was interested in something a little different: the interior space of a young kid's head." Carter regards the hustler's tale as a metaphor for human struggle. "It was the site of my moral education, as strange as that may sound," he writes.
Monetary success, when it comes, merely paves the way for struggles of a different nature - the officers of the NYPD, who stakeout shows and trail rappers in broad daylight, or the Grammy Awards, who keep the hip-hop winners off the television even as they storm the Billboard charts.
Decoded made its debut at number three on the New York Times Best Seller list for hardcover non-fiction books, behind Laura Hillenbrand's Unbroken and George Bush's memoir Decision Points. It came in at 18 on the US Today list, achieving a relatively disappointing 54,983 sales in the US in its first two weeks, but reviews have been broadly positive: The New York Times praised it for its "survivor's appraising sense of character" while The Observer called it "a book as revealing in its way as Bob Dylan's Chronicles or even Charles Mingus's Beneath the Underdog."
The writing is confident, but short on braggadocio. In one anecdote, a Village Voice journalist takes him to task for wearing a Che Guevara T-shirt with a platinum chain. Many would dismiss such a criticism out of hand, but Carter muses on Marxism, materialism and the struggle of the dispossessed for 10 paragraphs; this is not a man afraid of self-analysis.
Jay-Z, of course, has cleared every barrier placed in front of him, and his headline performance at 2008's Glastonbury seems to confirm that modern hip-hop knows no glass ceilings. Perhaps it is a by-product of Carter's place in the mainstream that Decoded's musings on Hurricane Katrina, Barack Obama and Noel Gallagher add little to the familiar media narrative. But really, the value of Decoded is in its musings on hip-hop itself: as an art form, as a communication of the black American experience, and as an outlet for youngsters with a pen, a mic and a story to tell.