Prelude76's review actually summarizes the story rather well.
I'd like to add that I didn't expect this to be as good as it turned out to be. I expected a rather low-quality comedy (as in a B movie if not worse), but the acting, directing and dialogue was surprisingly well done.
I love Brolin, and Coogan is in fact to be discovered.
It is interesting to note that Jerry O'Connell has such a small role at the beginning that one must wonder why his name is even up here in the actors' credits. It's as though he had a leading or supporting role, he doesn't, it's merely a cameo appearance of 5 minutes if that.
Still a recommended movie for all murder/mystery/comedy lovers.
8/10