Tolkien Legendarium

I'll start this off with a cult classic

Tolkien's legendarium consists of his various works and pieces revolving around the history of Arda, where Middle-Earth is located (Arda is the planet)

The main piece is, of course, Lord of the Rings. This is a very good book to anyone willing to read it. It's a bit packed with description, but Tolkien does not disappoint in the beautiful earth he has created.

The other main piece is The Hobbit, which takes place some years before LotR. This is far more of a children's book, and is a good starting point for anyone looking to get into Tolkien or literature as a whole

Finally, the other main piece is the Silmarillion, a collection of Elven legends that begin with the birth of Arda, down to the wars between the Elves and Morgoth, which is kind of like Satan.