The Silmarillion
by J.R.R. Tolkien and Christopher Tolkien
on the S from KingmakerS
This is what you might call a prequel to Lord of the Rings since it is set in a time before the Ring in what the people of Middle Earth call Elder Days. If I remember correctly it was unfinished when Tolkien died. It is on my shelf, somewhere, to read.
The Kingmakers is also waiting to be read.