When I was DS's age (9), I loved Mallory Towers, Rider Haggard, Austen, and other bits and bobs.
Just ordered Rider Haggard, White Fang and Sherlock Holmes - any other thoughts? He's very much not an Austen kinda guy.
Thinking along the lines of Day of the Triffids, The Chrysalids, 1984 - all too scary for him? Animal Farm p'raps?
Am out and about today but v grateful for suggestions, will check back later.