What great novel sounds really dumb if you try to sum it up quickly?

A lot of the greatest science fiction movies and TV shows have concepts you can sum up in a sentence, and it will make total sense. But books? Many of the greatest novels just sound ridiculous if you try to explain them in a single breath. What's your favorite science fiction or fantasy novel that can't be summed up without losing the magic?

Please include a book cover or other image for your chosen book. And mention the title, and why it's too complicated or clever or awesome to be explained in a single sentence. Thanks!

Top image: Starship Troopers by Robert A. Heinlein, chosen partly just because it's an amazing image.