The Voyage of the Dawn Treader by C.S. Lewis
I did read all of the Chronicles of Narnia books when I was young, but I don't really remember much of them. Before the first movie came out a few years ago, I started to read The Lion, the Witch and the Wardrobe to the kids, but I found it wordy and kind of boring, so we didn't finish it. Then, when Jon happened to see a trailer for The Voyage of the Dawn Treader, he made a declaration that anyone who would like to see the movie would have to have read the book first. I knew the younger kids wanted to see it, and I wanted to give a Narnia book another try, so I read it out loud to the three youngest. Happily, it turns out that it is a great book.
I think it helped that Eustace, the nasty cousin, is so delightfully nasty, and that parts of the story are told from his point of view, via a journal he keeps. The story moves quickly and there are plenty of exciting and interesting adventures. But mostly I loved the religious symbolism in the book. Eustace's recovery scene (I don't want to ruin it for anyone who hasn't read it) is especially wonderful. I thought about it off and on for days after reading it. I really loved the book.