Hmm let's see:
"The Hobbit" by Tolkien is amazing. The writing holds up way better than in the LOTR trilogy and it's a great fantasy adventure.
"11/22/63" by Stephen King. It's not an horror, but a mix of historical fiction/scifi regarding the Kennedy assassination. It's one of the absolute best King's books.
"Project Hail Mary" by Andy Weir. It's a captivating scifi adventure grounded in real science, Weir is very good at explaining scientific concepts and ideas so don't worry about it if you aren't into science, it's an easy read. If you liked the Martian (film or book, they are similar) you'll 100% like this one too. Avoid spoilers at all costs.
"Eragon" by Christopher Paolini. I've read it when I was a teen, so I don't really know how it holds up now, but I remember it fondly. It's a YA fantasy saga, very enjoyable.
"The Warlord Chronicles Series" by Bernard Cornwell. An historical fantasy saga that I read years ago and it's well-regarded in the genre.
Most of the stuff that I read is scifi/horror, so if you ever want to read something in that realm come back to me hahaha