I love books and tv and movies that are timeless. like, as in I can barely tell when they were made. I just read the sequel to Ratha's Creature and it was published in 1984. 1984. It's just Warrior Cats but a little more mature and with a made up species of cats and no humans and stuff. I thought it'd be from, like, 2012 or something. It's set before humans (I just ignore that I believe humans have been around only a day less than all the animals) so you don't realize that the technology was nowehere near as advanced as it is now or anything.
Another timeless book is The Giver (and its sequels). I didn't realize how old they were until later too