Title the book after one of the main characters like "Robinson Crusoe" by Daniel Defoe or "Herzog" by Saul Bellow.
Use a catchy phrase or a play on words. "To Fetch A Thief" and "Thereby Hangs A Tail" by Spencer Quinn are just two examples.
Use an important phrase from the book as your title. Margaret Mitchell obtained the title "Gone With the Wind" from a phrase spoken by Scarlett O'Hara in the middle of the book.
Make your title short. Long titles are easier for readers to mix up when requesting the book.
Refer to an important location in your book for your title like "Wuthering Heights" by Emily Bronte.