Since the ceaseless 'making' of his world extended from my father's youth into his old age, The History of Middle-earth is in some sense also a record of his life, a form of biography, if of a very unusual kind. He had travelled a long road. He bequeathed to me a massive legacy of writings that made possible the tracing of that road, in as I hope its true sequence, and the unearthing of the deep foundations that led ultimately to the true end of his great history, when the white ship departed from the Grey Havens.So I have come to the end of The History of Middle-earth, with this volume. The first two-thirds are about the composition of the appendices of LotR; the rest brings together some short essays, mostly unfinished. Two of these are rather interesting. "The Shibboleth of Fëanor" looks at how the original 'þ' became 's' in Quenya but remained 'þ' in Sindarin, as in the name Sindacollo, the Quenya version of Thingol; Sindarin itself is a Quenya word, the Sindarin calling themselves the Egladhrim. There is also an intriguing late set of thoughts on the true identity of Glorfindel, who appears in quite different contexts in both LotR and the fall of Gondolin; one fascinating possibility is that he actually was killed in the First Age but allowed to return from the Halls of Mandos to accompany Gandalf on his mission, which would explain why the Nazgûl are particularly perturbed by him.
There is also the fragment of The New Shadow, a sequel to LotR which clearly wasn't going anywhere; it is a story of boyhood orchard-robbing near Minas Tirith which didn't quite come together. It's been rather instructive to see the number of false starts Tolkien made on what might have been substantial works - The Lost Road, The Notion Club Papers, and his various attempts, all pretty unsuccessful, to tell the story of Ëarendil. These are not journeyman pieces; they were mostly written when Tolkien was already a published author. Fortunately, of course, he had the luxury of abandoning lines of writing that were just not working out (though he went back to Ëarendil several times over). But it's worth remembering that many good pieces of writing have quite a lot of less good writing from the same pen behind and below them, most of which we readers will never see.
Most people will either buy all twelve volumes of The History of Middle-earth, or none of them. My recommendation for the curious is to try the tenth of the sequence, Morgoth's Ring, with its essay on elf sex among other interesting fragments. As for me, I've got John Rateliff's two volumes about The Hobbit on the shelf, and a few other bits of Tolkieniana; so I shall not get bored.