Sorry Tharlionglin, I didn't understand that you knew nothing about the Letters
Humphrey Carpenter published a collection of letters sent by Tolkien, in the book
The Letters of J. R. R. Tolkien Here you have a link to this book in Amazon:
The Letters of J. R. R. Tolkien
It a very interesting book. In these letters Tolkien explains a lot of things about Middle Earth that cannot be found anywhere else, and it is also a very good source for knowing him better