The book about Robert Enke is worth reading. As a previous poster said, not enjoyable, given the subject nature, but moving.
I would also recommend Coming Back To Me: The Autobiography of Marcus Trescothick. Very honest book.
Just finished reading I am Zlatan Ibrahimovic. Very honest and interesting read. Best autobiography I have read in a long time.
My Father And Other Working Class Football Heroes by Gary Imlach is one of the best football books I have ever read.