The Silmarillion by J.R.R. Tolkien. Published posthumously by his son. Tolkien died before he could finish it.
A bit dry, perhaps, but worth reading for anyone who read and really liked
The Lord of the Rings. Sort of the Bible of Middle-earth. Though Tolkien might appreciate "saga" more than "Bible."
I'm just starting
The Rangers at Dieppe: The First Combat Action of U.S. Army Rangers in World War II by Jim DeFelice. Found it on Amazon several months ago in hardback for only $1.30. So even if it's terrible, I'll be able to say I got my money's worth.