I love horror movies, TV series and books, probably my favourite genre! I have so many recommendations (you'll have seen/read some before I'm sure) so brace yourself lmao
Film: Halloween, A Nightmare on Elm Street, Friday the 13th, Scream, The Exorcist, Zodiac, Jaws, Poltergeist, The Evil Dead, Texas Chainsaw Massacre, The Thing, The Omen, Psycho, The Lost Boys. The Silence of the Lambs is my favourite film of all time, it's more of psychological thriller but SO good. As you can tell I prefer the classic stuff to more modern films but there are some recent horror movies out there that are worth a watch.
I don't tend to read many horror books but I'm obsessed with true crime. Apart from that the Hannibal Lecter series by Thomas Harris is great - Red Dragon, Silence of the Lambs, Hannibal and Hannibal Rising. So well written. There's a few book versions of horror films/TV shows that I'd recommend too - Mindhunter, The Exorcist, Zodiac.
TV series: Mindhunter (favourite ever, could talk about it all day), Hannibal, Scream, American Horror Story (the first season mainly), Bates Motel.