Robert James Fischer is the most controversial of the World Chess Champions. He had an immeasurable influence on chess: opening theory, the format of the World Championship, prize funds, the Fischer clock, and Fischer Random (Chess 960) chess.
My 60 Memorable Games is required reading for any serious chess student. Garry Kasparov dedicated one volume of his series, My Great Predecessors, to Fischer (Part IV).
Numerous books have been written about Fischer, the man, and his games. The most recent work is Endgame, by Frank Brady, which takes a close look at his rise to greatness and his subsequent fall to the "edge of madness".