No haven't read the book so I can't help you there. I'm a Johnny Depp fan though and I've been waiting for him to get off the Pirates kick and do something new for a while now. Johnny's voiceovers in the trailer reminded me almost of Ray Liotta's in Goodfellas but with a Hunter S. Thompson bent.
I have read Fear And Loathing In Las Vegas and enjoyed the hell out of it! Much more so than the movie.