I also get the impression that he's in the process of teaching himself to read, which is probably very stimulating to his little brain. Part of me hopes that when he learns to read a bit, he won't need as much constant input from me - but that's probably awfully optimistic!
Reading didn't help at first, but when DS mastered reading chapter books I got some much needed pockets of quiet time. I remember buying him the Magic Tree House Boxed set for his kindergarten "graduation" present and I barely heard from him for a couple of weeks. I was actually excited when he got done and came back for input.
I think he still (at 9) needs a lot of input and we both prefer that much of that come from meaningful interaction. But the books buy us down time. So it does get a little better.
