The Way Things Work (http://www.amazon.com/dp/0395428572/) and pretty much any book by David Macaulay (http://www.amazon.com/David-MacAulay/e/B000AP72G0/)

The Stars, A New Way to See Them, by HA Rey (author of Curious George) (http://www.amazon.com/dp/0395248302/)

and another collection (not intentionally for boys) over on Edward Tufte's site: http://www.edwardtufte.com/bboard/q-and-a-fetch-msg?msg_id=00018v