None of my family were remotely interested in Tolkien. They were readers but just not their thing so I was a blank slate pretty much. I saw the Jackanory Hobbit, and had to read the book to find out what happened as I missed the last episode. I remember crying at Thorin's death. However I might just have been a bit dim.. when I read the LOTR a few years later I didn't twig that the title of the third volume was a bit of a clue to the outcome... Actually it is probably just as well that my Dad wasn't remotely interested in Tolkien given how he reacted when he discovered I was riveted by the Day of the Jackal because I wanted to know if the assassin succeeded...
These I seldom read a book I don't have an idea about from a review or browsing though last year "We are all completely beside ourselves" was one since I was given it and it was a particularly good one to read in initial ignorance.