Word Freak
Stefan Fatsis' book about competitive Scrabble, Word Freak, could perhaps have been subtitled, "You don't have to be crazy to win Scrabble championships but it helps." Fatsis tries to warn us against drawing too many conclusions about the relationship between genius and madness from his book and it seems pretty clear that he writes more about the colorful eccentrics (and worse) in the game than the players who lead more balanced lives. Still, whether you've got a layer cake of seven personality disorders and a touch of psychosis on top or not, it seems you must share some traits in common with the obsessive-compulsive to do what it takes to be a top-flight player. Memorizing lists of thousands of words sorted by the tiles in a Scrabble tray which could be used to make them (while generally avoiding their meanings as a waste of grey matter) is just a start; then come questions of strategy, endurance, and the ability to think under pressure.
Fatsis went first-person by taking up competitive Scrabble himself, a perspective which offers a more sympathetic view of some of the more wacko players than if the book had been written at a greater distance. A writer about sports and business for NPR and various national magazines, Fatsis ably covers the history of Scrabble and its business angle as well. The book is fascinating and funny, although it might have been edited down by 10-20% and been even better; its only drawback is a few dry patches where it feels like you've got to be obsessive yourself to carry on.