I downloaded Muay Thai: The Art of Fighting e-book a while back (http://fliiby.com/file/41508/qzfh9t3bvw.html ) and it seems pretty good. I have yet to read it but from skimming over it, it seems packed with useful information. Also I've heard good things about Muay Thai: The Most Distinguished Art of Fighting book. I plan on getting it one day...