It's okay to disagree with your friends or loved ones about certain things. But still, some things are sacred. Which science fiction or fantasy book is so essential, you'd refuse to be friends with (or to date) someone who didn't like it?
Please include a book cover, book trailer, piece of fan art, or other visual representation of the book in question. (And if it's fan art, please name the artist and link to their site.) And please mention the book's name, the author, and why you'd end a friendship or walk out on a date over it. Thanks!
Top image: Consider Phlebas by Iain M. Banks, French edition. Not everybody has read this book, but when I meet someone who's read it and not loved it, I back away slowly. Also, Geek Love by Katherine Dunn, The Dispossessed by Ursula K. Le Guin, and a few others.