No kidding.
I have tried to learn all I can know about the history of Middle-earth (speaking both internally and externally) and have collected almost all of the works related to it, save some few which are either difficult to get hold of or which I've no real interest for.
As it stands, I have: Multiple versions of The Silmarillion; The Letters of J.R.R. Tolkien, a companion-piece to his Biography and with much information on the composition and history of Middle-earth; the entire History of Middle-earth Series, mostly in one edition; and the Narn i·Chîn Húrin, or Tale of the Children of Húrin in a first-edition copy.
I've often found myself an apologist on the behalf of Christopher Tolkien. Having read through the History of Middle-earth Series and other works, I can say with much certainty that I not only agree with many of the editorial decisions he made, but also that I would have made them myself, usually with the same intentions, (whether mistaken through oversight or justified through other textual-evidence).
LOL
Well, it took me a few years to know as much about Tolkien and his mythologies as I do - not that I know everything, but I know alot - and it isn't all that difficult if you set out to discover it all. The major difficulty is getting all the works into one place, collecting all the books related to Tolkien and the matter of Middle-earth. It's taken me well over five years to collect what I have now, and it still isn't near complete. LOL.