Big List. Easier to list what he already has and add extras.

Obviously

James Corbett books
Anderson's books

Tahawar Ali Khan - "Maneaters of the Sunderbans" - rare expensive book, but I managed to find one at a better price.

http://forums.nitroexpress.com/showflat.php?Cat=0&Number=104782&an=&page=0&vc=1

If you do a search there is already a lot of suggestions:

http://forums.nitroexpress.com/showflat.php?Cat=0&Number=49736&an=&page=0&vc=1

"Eight Years Wandering in Ceylon" by Samuel W. Baker
http://forums.nitroexpress.com/showflat.php?Cat=0&Number=26783&an=&page=0&vc=1