Camino Ghosts by John Grisham

Mercer Mann, a popular writer from Camino Island, is back on the beach, marrying her boyfriend, Thomas, in a seaside ceremony. Bruce Cable, infamous owner of Bay Books, performs the wedding. Afterward, Bruce tells Mercer that he has stumbled upon an incredible story. Mercer desperately needs an idea for her next novel, and Bruce now has one.
The true story is about Dark Isle, a sliver of a barrier island not far off the North Florida coast. It was settled by freed slaves three hundred years ago, and their descendants lived there until 1955, when the last one was forced to leave. That last descendant is Lovely Jackson, elderly now, who loves her birthplace and its remarkable history. But now Tidal Breeze, a huge, ruthless corporate developer, wants to build a resort and casino on the island, which Lovely knows, deep down, is rightfully hers.
Mercer befriends Lovely, and they plunge into an enormous fight over who owns Dark Isle, taking on Tidal Breeze Corporation, its lawyers, lobbyists, and powerful Florida politicians. But Lovely knows something about the island that could seriously cloud the dollar signs in the developer's eyes: the island is cursed. It has remained uninhabited for nearly a century for some very real and very troubling reasons. The deep secrets of the past are about to collide with the enormous ambitions of the present, and the fate of Dark Isle--and Camino Island, too--hangs in the balance.