Something I'll be looking into buying for myself is the entire Dragonriders of Pern series by Anne McCaffrey, and also her Acorna series. She writes high fantasy and science fiction novels, dating back to the late 60's.
Another great author is Anne Rice, she wrote the Vampire Chronicles, including titles like Interview With the Vampire, Queen of the Damned, and has an erotica series based on a fantastical interpretation of Sleeping Beauty. Somewhere along the years she became a Christian and began writing Christian novels too, if you're interested in that.
Clive Barker is a great author, he created the Hellraiser series, if you're into classic horror.
Anything by H.G Wells, he's a renowned classic author. Anything by J.R.R Tolkien, and if you're wanting true-world dystopia, 1984 by George Orwell.
The Eragon series by Christopher Paolini is still good, even if the movie adaptation was hot garbage.
John Carter of Mars by Edgar Rice Burroughs is a great series for those who love science fiction/fantasy, it's basically a space opera.
Morgan Llywelyn is a great Celtic writer, my favorite book from her is The Horse Goddess. Tells a mythical story of the Celtic goddess Epona and her "supposed" origins based on the creative mind of Morgan.
Just some picks, I could go on for days.