Books: my DS loves/d (come to think of it, he doesn't use them so much now at 8.5, I think because he has memorised them) the Usbourne Dictionary of series, especially the
Dictionary of Chemistry. Despite the name, it's not a dictionary, and has loads of illustrations. The fonts are small, but that's pretty common with highly-illustrated books - my guess is these would have the right tone. They have lots of information, and I guess are principally supposed to be revision aids for much older children.