I coincidentally borrowed this book from a friend the day Iain M. Banks died, which is fitting, as this is a book with "suspension of disbelief"-straining coincidences. It's also galaxy-spanning hard science fiction, philosophy and "suspension of disbelief"-straining space opera. And it's pretty brilliant with a new revelation around every corner.
Aside from the stuff already mentioned you may struggle with the way you're occasionally dropped into the main timeline's distant past without warning and without obvious markers. You're just 'now' in one paragraph and suddenly 'then' in the next, and have to realized that all by yourself by what's happening to the main character, where it's happening and whom he is with. On at least one occasion I was in doubt for several sentences before realizing that I hadn't been taken into the past, but I learned to like this. And you may struggle with the complexity of the world it's happening in, as things are often mentioned in the passing and barely explained or not explained at all, but I liked this as well.
Oh, and don't expect a Culture novel. This isn't one. But if you like Banks in general, and like new experiences in general, this is a novel for you.