Unless you are interested in 50-Cent, the book does not add much to the 48 Laws. Robert Greene is a master at finding anecdotes to -cough- proof his 'laws', and 50-Cent's life seems to be a good source for those.

More cynically, the book seems a bit like a marketing ploy to reach a different demographic for his books - I can almost imagine kids running around with "48" tattooed in big Fraktur letters on their upper arms..