I found the 1930s difficult, but Brave New World was a great read that I had never read (hangs head in shame).
I've got Dahl on next year's challenge required reading list, although it's Dahl that's not for kids. Next year is more modern, but was still difficult to compile. You can see the current list of books in my signature.
Reading Lists: 2011 | 2012 | 2013 “Reading one book is like eating one potato chip.” - Diane Duane