If you're into fantasy, look into The Wheel of Time series. It's dense, absolutely packed with characters, and the world has a ton of detail. It's also 14 (rather large) books long, 15 if you count the prequel, so if you like it it'll keep you busy for a good long while.

If you've seen the Amazon series based on the books and were turned off by it, maybe give the books a try instead. The Amazon series doesn't do it justice, in my opinion.