As the book this is a quite intricate film, whit many plot twist and flashbacks. To follow precisely the whole plot you need to be focused a hundred percent on the movie, because everything happens quick.
The acting is on a really good level (at least in Italian). The direction and screenplay are fantastic, here and there during the movie you can find some beautiful glimpses of Lago di Garda, where the story is set.
Being Carrisi both the writer of the book and the direcor it is impossible for the movie bot to be precisely coherent with the book.
I would really recommend to watch the movie and then read the book (which is a lot more detailed), if you haven't already done it!