Forum:The Books of Middle Earth

Hi there. I've just become a member and would like to ask you something.

Which books does someone have to read if he/she wants to learn everything about the Middle Earth? Silmarillion, LOTR, The Hobbit, Akallabeth And Of The Rings of Power, The Children of Hurin are simply OK. What should be read apart from these above? I heard that there were some letters which were sent by the fans of Tolkien and answered by him. I think I saw on the web that it was gathered together and published by someone. Besides, I saw people talking of some books too. As far as I remember, one of them, The History of Middle-earth, belongs to Christopher Tolkien. The name of the other book is The Complete Guide to Middle-earth.

My question is, is there any books about Middle Earth that I forgot to mention? If so, please let me know. From time to time, I read many articles written about Middle Earth and notice that the references below the pages can be various. I did not want to search the web for I believed it would be hard to find them that easily and decided to ask this simple question here...I hope you will help me. Thanks for your replies in advance.