I always get such a sense of place when reading Lehane's books. Whether it's the streets of Boston (Kenzie and Genarro), or Miami and Cuba (Joe McCoughlin), I really do feel as if I'm there.
And this book is no exception. I've visited a few of the Boston Harbor islands that are mentioned here and I can certainly picture the fictional Shutter Island.
I'm reading this one for my 'Set in New England' square, but seeing how a patient has seemingly just vanished from a locked prison cell, I reckon it could count as a 'locked room mystery'.