A source-criticism analysis:
Experts in source-criticism now know that The Lord of the Rings is a redaction of sources ranging from the Red Book of Westmarch (W) to Elvish Chronicles (E) to Gondorian records (G) to orally transmitted tales of the Rohirrim (R). The conflicting ethnic, social and religious groups which preserved these stories all had their own agendas, as did the "Tolkien" (T) and "Peter Jackson" (PJ) redactors, who are often in conflict with each other as well but whose conflicting accounts of the same events reveals a great deal about the political and religious situations which helped to form our popular notions about Middle Earth and the so-called "War of the Ring.". Into this mix are also thrown a great deal of folk materials about a supposed magic "ring" and some obscure figures named "Frodo" and "Sam". In all likelihood, these latter figures are totems meant to personify the popularity of Aragorn with the rural classes.
Because The Lord of the Rings is a composite of sources, we may be quite certain that "Tolkien" (if he ever existed) did not "write" this work in the conventional sense, but that it was assembled over a long period of time by someone else of the same name. We know this because a work of the range, depth, and detail of The Lord of the Rings is far beyond the capacity of any modern expert in source-criticism to ever imagine creating themselves.
Hat tip: VoxDay