When the literature was written has little bearing on whether or not it should be studied. You are nothing without your history. You are, at best, misguided to ignore it.
Yes it can be distilled into, "We are all two meals away from barbarism", but the process documented in LOTF is is fascinating. The language isn't anything other than correct though the colloquialisms are a bit jarring.
Remember to study how the book is constructed too. Don't just focus on the content.
J.R.R. Tolkien is older than the other books you quote, and the author himself was "older" when he wrote the Middle Earth books, though they are the culmination of a life dedicated to linguistics and philosophy. The thought processes behind LOTR predate anything that people alive would recognise as a "modern" attitude.
Stephen King can't write. He is a stolid workman, plodding through a series of formulae. He very seldom explores anything new. Dan Brown can't write either, and I would suggest that the NCEA student who wallows through The Da Vinci Code would have to be a P or crack addict to stay awake.
Animal Farm is one of THE most important works of the 20th Century. It is thoroughly subversive, more so today when there are MORE Government controls in place than when it was written. Social fabric was determined by class when Animal Farm was written. Class is a state of mind, a series of subsets of a philosophy that again is foreign to our culture but intrinsic in its creation.
Terry Pratchett parodies modern "British" culture. Without an understanding of the nuances of that culture today, you can miss stuff, but how does it help you understand your own? Satire relies on the reader having an intrinsic understanding of the subject being satirised. I love Pratchett, but I know a lot of people who don't get it. They aren't stupid, large chunks of his books seem like a very weak parody of Fantasy literature, rather than social commentary, because their experience of their own culture and society is very different to the intended reader.
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