I haven't read the book, but I found this entertaining.
The movie was funny. It had its moments of seriousness too. It had everything a film needs. It had good guys, bad guys, guys you weren't sure were good or bad, and a smokin' hot love interest. It also had some very visually stimulating scenes, and it really gave us a good insight into life in Puerto Rico.
Giovanni Ribisi probably gave us his best role since Saving Private Ryan, and Johnny Depp actually played someone who appeared to be a half-normal human being.
How many times have I told myself that I'm never going to drink again?