A prior book discussion:
http://www.net54baseball.com/showthread.php?t=219942
My top choices would be:
-Pigskin
-Breaker Boys
-The Games That Changed the Game (I think the OP will like the Sid Gillman chapter)
-The Sunday Game: At the Dawn of Professional Football
The book I read most recently was Ralph Hickok's bio of Johnny Blood (
https://www.amazon.com/Vagabond-Half...k+johnny+blood). Hickok knew Blood and travelled with him, but agreed not to publish the book until after his death. It was excellent.