Some of the best are 'Ender's Game' by Orson Scott Card. It delves into themes of leadership, war, and morality in a science - fiction setting. 'The Wheel of Time' series by Robert Jordan is another great fantasy series. It has a complex magic system, a large cast of characters, and an epic story arc spanning multiple books. Also, 'Foundation' by Isaac Asimov is an amazing science - fiction work. It presents the concept of psychohistory and the fall and rise of a galactic empire.
One of the best is 'Dune' by Frank Herbert. It combines a richly detailed desert planet, complex political intrigue, and a hero's journey. Another great one is 'The Lord of the Rings' by J.R.R. Tolkien, which has a vast fantasy world filled with magic, different races, and an epic battle against evil. 'Hyperion' by Dan Simmons is also excellent, with its unique blend of science fiction concepts and a story told through multiple perspectives.
Well, 'A Song of Ice and Fire' series by George R.R. Martin is a top pick. It has a huge and detailed world, full of political machinations, complex characters, and unpredictable plot twists. Then there's 'Neuromancer' by William Gibson. This novel is a classic in cyberpunk science fiction, exploring the ideas of virtual reality and a dystopian future. 'The Hitchhiker's Guide to the Galaxy' by Douglas Adams is also a must - read. It's a hilarious and imaginative take on science fiction, with absurd situations and memorable characters.