Crucible of Gold, by Naomi Novik

Laurence and Temeraire are relatively content on their isolated property in the Blue Mountains of New South Wales, when a familiar British diplomat literally drops in. Bonaparte has allied with the Tswana with designs on South America and so the draconic duo are to be (sort of) reinstated to the military to help head off the problem, because of their African experience. Of course nothing goes smoothly – shipwreck, marooning and mutiny are just the start of their obstacles. The Incan Empire offers a whole new take on human-dragon relations, as well as a new phase in the Napoleonic wars. By helping in Brazil, Britain gains Portugal’s friendship. But shifting alliances put Laurence’s reinstated captaincy at risk and it seems he and Temeraire may be returning to China for their next adventure.