Does he like the DK one subject encyclopedias? DS loved that shelf at the library, particularly one about religion all over the world.

There are picture books with lots of words, like the Dinotopia series, you might try.

There are also comics you might try to get him hooked on - Calvin and Hobbs, Peanuts. My son is currently enjoying the web comic 'KXCD' i think it's called.

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