I enjoyed Word Freak
while I was reading it, mostly because I'm a language-nerd-wannabe. It was interesting enough, and I enjoyed watching Fatsis become more and more involved in the world of professional Scrabble. Plus, I picked up some excellent words to use when I play.
In retrospect, the book as a whole went on a little too long, and I had issues with some of Fatsis's descriptions of other players. However, I would still recommend it to anyone who plays Scrabble for fun (and also likes reading, of course). If nothing else, you'll be able to modify a few of the strategies more advanced players use to help your own game out, and you should be able to find at least one useful word you didn't know existed before you read Word Freak