I found The BGF by Roald Dahl at the thrift store and remembered how much my oldest son liked it. So I bought it for 99 cents and have been reading it to my younger kids. We have been enjoying it, though I have to say that it is a bit hard to read out loud as the giants talk very oddly and mix up words and such. Brennen remembers reading it too in elementary and has been sitting in on our reading sessions occasionally.
The other thing that is fun is that Dustin and the little kids talk about it with each other--the part the little kids just read, funny parts, the biggest giant, etc.
How to connect teenagers to little kids? Read a favorite book.