"Consciousness is the process of simulation of reality" is a starting point. The question is asked "How does the simulation work?" Why are we so good at simulating certain kinds of counterfactual scenarios? Why do we consider some to be plausible (e.g. worrying about a friend moving away) while others we disregard as immediately absurd (e.g. worrying about being attacked by pink nerve-gas-farting dragons)?

Like most of his books, it's a great yarn in an interesting world. The ideas he's exploring are rooted in platonism (how can a theoretical mathematical abstraction affect physical systems?), quantum physics, and the nature of consciousness. It takes a while to really get rolling, and when it does it snowballs fast, but I found it to be very enjoyable from the start.