With Proud Humility by Jess Mountifield
This was almost pure research. I'd never actually been but I watched a few well researched films on the subject as well as studying the Caribbean from both the piratical side and the side of English colonists. On top of that it was surprising what I managed to pick up from reading other books written in the same time period. Even one of Jane Austin's novels mentions the Caribbean and gives an insight to the general social standing there etc. To make sure I had got most of it right I also had someone proof the book who'd both lived in the Caribbean and had a history degree.