The Greatest Game Ever Played. (About the Harry Vardon/Francis Ouimet U.S. Open). SO much better than the movie (which was a Disneyfied travesty).
Anything by John Feinstein, but especially Open, and A Good Walk Spoiled.
Slow to Get Up, by Nate Jackson
Ball Four, by Jim Bouton
A Whole Different Ball Game, by Marvin Miller (more about baseball labor than baseball)
Curt Flood’s book about the same topic (I can’t remember the name of it right now)