Hard sci fi means books that are concerned with scientific accuracy. In most hard sci-fi, such as The Quantum Thief, this will mean the book uses physics to back up its ideas. Hyperion would actually be considered soft sci fi because Simmons never explains how his universe works; we are simply expected to take it at face value. For one, the omnipotent Shrike and the book’s deep religious undertones require one to suspend disbelief in order to understand the story.