One of my 8-yr-olds has decided that reading is his favorite thing and he's looking for some new books. He's reading at the Magic Tree House, Boxcar Children level. He enjoys "action or adventure" type books. He loves to listen to the living books we read for history and science, but for his free reading he wants "stuff that's fun and not boring." He's also looking for books a little longer than Magic Tree House (I think he wants to feel more grown up) and series are cool too.
Thanks for any help you can give.