I've found a pretty slim selection of hunting story ebooks, but there's a couple of free ebooks at
www.gutenberg.org with hunting/adventure themes. Lots by Roosevelt. This site carries free ebooks who's copywrites have expired - lots of old classics.
A real good one there is 'The Man-eaters of Tsavo' by Col. J.H. Patterson written in 1907.
Also, in August, Amazon is releasing William Faulkner's 'Big Woods, the hunting stories of William Faulkner' in ebook format. This book was highly recommended by Bob Scammel in the most recent AO magazine.