What are those books that never get old no matter how many times you read them. My list is the following.
1. O'Brian's Aubrey Maturin series.
2. Just about anything by C.S. Lewis, but particularly his non fiction theological stuff.
3. Tolkien. Ok, not just one book, but pretty much the whole lot of it.
There are a few others, but those are at the top of the list for me.