Culture, the dominant empire in the known universe, is an interesting place. People have fully tamed their hormones, able to secrete anything at will, change genders, heal wounds. Machines and humans co-exist with mutual respect. Tiny drones and intergalactic starships are independent, intelligent entities with personality. Humanity has broadened: it's not just homo sapiens, but many many other kinds of humanoids from all sorts of different planets. Mysterious superintelligent Minds (presumably machine) that seem to run the system. How does Culture interface with other civilizations?

This book is definitely a page turner: great story telling, with an air of mystery throughout.