The stories of Middle-earth are really one book, and writing it took Tolkien all his life: and unawares. Despite much polishing after writing, he seems not to have planned, so much as discovered, what he has to say. The Hobbit grew from a single sentence, and he had apparently no idea what a hobbit was or how to finish the book. Similarly with LR: the introductory note to Tree and Leaf (1964–5) describes

The story itself is cast as active, the writer as passive. Suggesting himself as a heroic hobbit on a quest, with companions (‘we’), could be disingenuous, a conceit which orders untidy experience and implies the story as somehow independent of its redactor. (Later he was to authorize his own fiction by posing, in its preliminaries and appendices, as merely its editor – a further fiction.) But this suspicion need not destroy the essential honesty of Tolkien's consistent description of how he wrote. For what starts as an apparently trivial children's story, faltering in tone and clumsy in writing, does seem unpremeditatedly to collide with the world of The Silmarillion about half-way through, and the seriousness with which Tolkien was taking his story seems to rise with the rhetorical level (one might recall Lewis's remarks in ‘On Stories’, 39). Much in Tolkien's letters supports the Tree and Leaf account of the composition of LR. Moreover, he kept recasting earlier material in version after elaborated version. So there is more than a grain of truth in presenting himself as an editor: he is indeed editing and reinterpreting the work of another man, that self he was when first he created those stories.

His sources – if ‘sources’ is the word – are only the stones that form the tower: Tolkien's warning should be heeded. But they range interestingly widely.