"The Silmarillion" by J. R. R. Tolkien is a collection of tales that make up the epic mythology that forms the background of "The Lord of the Rings" (LOTR), this book and "The Hobbit" are a must-read for anyone who wishes to fully appreciate LOTR.

I liked it a lot, though it was a bit tiring in some places and the abundance of characters and places was quite overwhelming. Having read all the three books, I now take back my earlier claim that Devakinandan Khatri's "Chandrakanta" and its sequels are better than LOTR as epic works of pure fantasy. Tolkien has created an astoundingly bigger and largely more consistent fantasy world, not to mention with much fewer arbitrary twists in the stories.