Big fan of Dennis Lehane since I read "Mytic River" a few years before the movie was released. "Shutter Island" was also an intensely captivating heavy plotline conveying some life parables that I found I was residually ruminating on for awhile after finishing the book..
IMO, unless you're talking a straight linear plot line romantic or action type flick, it's almost impossible for movies like these to capture and convey the book's multi-layered complex essence. Viewing them usually ends up disappointing me, although I knew that I might have felt different if never having read the book. ..so I'm gonna withhold my decision on whether or not to see it.
"Always remember that you are absolutely unique. Just like everyone else."