The first book homer picks up is The Bear Went Over the Mountain.
The is not a children's book, but is probably one of the funniest books of the last century, or decade at least. Written by William Kotzwinkle, the same guy who brought us the Fan Man.
http://www.amazon.com/exec/obidos/tg/detail/-/0805054383/002-0126487-6160808?v=glance
Martin