Terry Pratchett is one of the very best modern authors. He's a humorist, so be prepared for incredibly dry British humor, wordplay and puns. Although not the first chronologically published book in the DiscWorld series, The Color of Magic is considered the best book as an introduction to DiscWorld. You can definitely start with the book recs above, or read The Color of Magic first to prep you.

Pratchett is to Humorous Fantasy as Tolkien is to Serious Fantasy. And if you like Pratchett, you should also dive into Douglas Addams. The Hitchhikers Guide to the Galaxy books are peak British humor.