[Ibrîniðilpathânezel]

For my own part, I've read all of the HoME series, and in terms of providing the most information about the world we see in LotR, the Hobbit, and the Silmarillion, I found Morgoth's Ring and The Peoples of Middle-earth most enlightening (especially as a researcher and a fan writer).

The books that cover the evolution of the writing of LotR are interesting, but, IMHO, potentially confusing (the same can be said for the books that cover evolving and alternate versions of the Silmarillion). Looking at the variations and Christopher Tolkien's commentary can set one's head spinning, because sometimes, they raise more questions than they answer (well, that was my experience, some of the time, and I'm not unfamiliar with in-depth literary analysis). Unfortunately, there are a lot of questions that only JRRT himself can really answer, and even he hadn't made up his mind about some of them before he died. This doesn't mean I consider the books worthless; they certainly offer glimpses into the mind and method of Tolkien and his imagination, which can be quite valuable in appreciating his finished work. But I don't think it hurts for one to approach these books with care, if one is looking for more definitive information about Middle-earth, its history and its inhabitants. Just my two cents, of course.