Usually, the final installments of trilogies aren't very good. But the J.D. Stanton trilogy is one of those rare ones that gets better with practically every book.
When ol' JD volunteers to lead several juvie delinquents out to sea on a voyage designed to change their ways, the encounter trouble. Not in the supernatural kind, or at least not the supernatural you're thinking of.
They encounter a storm, and afterwards, they find themselves in a gray world in an old warship dating back to the 1800s. They eventually get on the warship, where the find nothing but ghosts. At this point in the plot, you just have to bear with it to find out what the ghosts really are.
The best thing about the end and explanation is that they don't have some kind of dumb demonic confrontation; it's just a normal end. This is one thing Gansky has improved on.
All in all, this book is worth reading once you get to the end.