It seems this film might have been more effective as a limited television series. There’s considerable narrative material that could have fleshed out all of the characters involved. While the movie succeeds in developing those individuals, it still conveys a sense of incompleteness; like you're only getting a brief look at their experiences. Since the movie is adapted from a book, I am now inclined to read the original story and discover if additional details are presented.

Source on TMDB