[Formendacil]

I will second the Garth recommendations (with my own evaluation that Tolkien and the Great War is the masterpiece of the two).

The anachronisms are an interesting case, because they're quite important for any analysis of what Tolkien is doing or desiring--there is SO much grist for the "literature is biography" mill in Sarehole and the Edwardian Age, etc--while also being largely the result of happenstance: i.e. Tolkien invents a new fantasy creature, the Hobbit, which really has a limited amount of lore in their self-titled novel: just enough to establish that, basically, they're Tolkien's default ideal of comfortable homebodies (i.e. his childhood personified). It's much more deliberate in The Lord of the Rings, of course--and much expanded--but it does stem from what feels like a much more happenstance decision in The Hobbit.

Although I generally agree with Tolkien's own, prickly, opinion that The Lord of the Rings really isn't about World War II in any obvious, content-based way (that I take his rejection of allegory quite seriously, because I think it doesn't work), there is still a reason that readers and critics were so quick to point to it, namely that the LotR is a work that could really only have been written in the 20th Century: Garth is very good on the ways that the LotR is very much part of the "WWI Poets" genre: a response to the horrors of that first war from someone who lived through it and digested it, and WWII does have its hand on the scales thematically: it's a book about the recurrence and inevitability of combating evil--an obvious theme to work into a book by a WWI vet during the second great war of his lifetime.

And that's without mentioning his environmentalism. Honestly, I sometimes think this is the TINIEST bit over-emphasised in discussions of Tolkien when he's mentioned in, say, media analysis, but it certainly is a major theme of the LotR: the destruction of Isengard's greenery, the would-be destruction of Fangorn, the desolation of Mordor, and the creeping desolation around it. This concern with the effects on the natural world by the works of Man (or Ork) is not exclusive to the 20th century, but it's certainly of a piece with it.