"Dry" by Augusten Burroughs.  I highly recommend it.

First of all, he's a really talented writer, and the book can be very funny and painfully honest.  I was just amazed that the guy even survived.  It really made me understand addiction on the emotional level.

There's one point near the end of the book that really wiped me out -- mostly having to do with dealing with emotions that the addiction covered over.