The third in The Ender’s Game series. I thought this one was rather good. There’s a bit of Chinese culture in there which gives things a different flavour. Borrowing from other cultures is sometimes a bit frowned upon in literature and art, but you need to get a bit of diversity into the lands of the future somehow. A number of sci-fi books have done well from this approach: Dune, The Man in the High Castle, Lord of Light to name a few.
This book once again has quite a different feel from the first two novels in the series. More politics, more epic. Having said all that I read the book a fair while ago and if asked to describe what actually happens in the book I’d be hard-pressed to tell you. Maybe Wikipedia?