Thinking that the length of some novels might be off-putting to him, I read him some of the short stories in Isaac Asimov's "I, Robot". He liked these but I could tell he was having a hard time keeping up. I think the wording of the stories was too advanced and there was too much talking and not enough action. Personally, I love Asimov, but I think much of it just went over his head.
Which science fiction and/or fantasy books would you recommend for an 8 year old? (Either stories he could read himself or that we could read together over the course of a few weeks.)