Crucible Of Gold by Naomi Novik

In an alternate Napoleonic-era world where dragons are integral to warfare, a British naval officer and his highly intelligent dragon companion are sent to the Americas on a tense diplomatic and military mission to secure allies and resources; they must navigate volatile colonial politics, the brutality of the slave trade, and rival European ambitions while confronting natural dangers, local resistance, and moral dilemmas that strain loyalties and test the strength of their partnership.

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