While not explicitly a psychology book, Ted Williams's THE SCIENCE OF HITTING offers great insight into the psychology of hitters, pitchers, and baseball generally. If I were a pitcher, after reading this book and thinking about the fact that the greatest hitter of his generation, if not in history, thought that he was successful if he got a hit once in every three at-bats, I would conclude that I possessed a HUGE psychological edge on any hitter, even the best, and would figure out how I could use that advantage in every at-bat.