Another book set in the universe of the Culture, Bank’s powerful, hedonistic galactic civilisation devoted to pleasure and doing good works. This one focuses on the machine intelligences of the Culture rather than the people, and makes it clear that the machines are people too, complete with virtues, vices, and erratic behaviour. “Excession” is hard work, but worth it. It’s a complex book with multiple plot threads and it’s stuffed with dazzling ideas. The Excession itself is an enormously powerful alien artefact/entity that appears and then simply sits there doing nothing; but by doing so it provokes a great many other entities into action they may regret. Banks has the writing skill to pull it off, but you really do have to be paying attention right the way through. It’s not perfect — there are a lot of ship characters in this one, not all of them clearly delineated by personality, and it’s very hard to keep track of who’s who at times. It does repay the effort, though. It’s funny, moving and thought-provoking, and holds a mirror up to ourselves in the same way the Excession does to the people and civilisations that encounter it.