Although this is a classic, it's one of the few older sci-fi stories that isn't too dated, as the setting is a post-nuclear war Earth at some indefinite point in the future and all the technology is vague and generically futuristic (like "skimmers"). It's the characters where Zelazny exercised his imagination. Earth is now overrun by mutants who resemble creatures out of myth, and the main character, Conrad, appears to be an immortal and may even be a god. He's a typical Zelazny main character: mysterious, complicated, immortal and superhuman but not invincible, and fundamentally heroic but kind of an asshole.
All of the characters are interesting in this book, especially Conrad's friend, the assassin Hassan, and I particularly liked the dialog and the action scenes. Zelazny has always been good at writing great fight scenes.
The story wasn't perfect -- a lot of things were just dropped in without explanation, and it seemed a lot of plot points were just handwaved away. But if you like Zelazny or good old fashioned science fiction written much better than most Sixties sci-fi, it's worth a read.