How to lose your reader or your viewer

My wife and I watched the first half of a movie the other night: Small Crimes, which is streaming on Netflix. It's based on a book by Dave Zeltserman which gets mostly rave reviews on Goodreads. (Usually with Goodreads, I find, you have to ignore half the positive reviews in order to get a real balance of views on a book, but that's by the by.) 

So it sounds like the book is worth reading, if you're into noir, and unreliable narrators, and subtle characterisation. The movie has a reasonab...