I'm a very avid reader and a football freak, i have loads of football books.
The best i've ever read is the book about Robert Enke from Ronald Reng (i have it in Dutch, don't know the title in English).
Some other very good ones:
Tim Parks: A season with Verona (outdated, but very good)
Joe Mc Ginnis: The Miracle of Castel Di Sangro (about the club from a tiny village in the Abruzzi who played in Serie B)
Feet of The Chameleon by Ian Hawkey (about African football)
Stamping Ground (Charlie Connelly): about Liechtenstein's national team and their qualification round for the WC in 1998 (wonderful book, really great).
Hard Yards (Nige Tassell): about last season in the Championship
Every football book By Michael Calvin is good (he as one about young players, one about talent scouts and one about managers, they are all 3 great).
Tears at la Bombonera (Christopher Hylland): about his journey about football in South America.
Jonathan Wilson has written plenty of very good football books, but the one i like most is "Angels with Dirty Faces" about Argentinian football.
The Quality of Madness (Tim Rich): about Bielsa before Leeds was in the EPL (not only Leeds, everything until the EPL).
Two other greats books By David Goldblatt: The Game of our Life (English football) and The Age of Football - The Global Game in the 21th century (an update on the one mentioned here, but not that good).
Football with the enemy (Simon Kuper) often cited as the best book about football ever.
Zonal Marking (Michael Cox) and alternative for Inverting the Pyramid (one can see it as a sort of update).
Two books by Michael Storey: 'Gazza in Italy' and 250 Days (about Cantona and the karate kick at Crystal Palace), every book about Cantona is great because he is such a fascinating person, and i'm not a Man Utd fan, far from).
Premier League, a history in 10 matches (a litle bit outdated, but great book).
Animals! The story of England v Argentina (Neil Clack): a totally different view about the clash at the 1966 WC. Fascinating.
For people who speak Dutch: Hard Gras (a literary magazine about football, great reads by excellent writers).
And also all the books written by Auke Kok.
Te early work of former Ajax player Jan Mulder is great too (he writes columns).