Morgoth's Ring The History of Middle-Earth 10

This book is the tenth part in a series of 12 books and contains Tolkien's rejected writings and notes which were later refined into the Silmarillion. It is in fact my favourite book of this whole series, because most of it seems to comply with the published works and explain a lot of the history of Arda; how the gods were created, how the world came to be, how Morgoth was jealous of the power of Eru and tried to usurp it, how the elves rose and fell; it is such a detailed resource. It also explains a lot of the culture and customs of the elves which is extremely useful when trying to understand their actions throughout the books; understanding their society and views helps to understand their priorities and actions which I find enhances the books tremendously.