This book offers, for me, the most understandable model of a narrative I've read so far. Chatman offers helpful concepts for analyzing both written and film narratives. He tries to create a synthesis of all narrative theory before his book, and he does a very good job. Instead of getting lost in a collection of different approaches, you actually find yourself connecting them all, seeing where they fit together.
Among all the books on narratology and narrative analysis I've read, this is the one most helpful not only for analyzing film narratives but also written narratives (although I would always recommend you also read "Narratology: An Introduction", "Narrative Fiction" and perhaps Bordwell and Thompson's " Film Art : An Introduction", if you want to focus especially on films).
This book and the way Chatman dissects the narrative are also interesting for people more interested in writing than in analysis: I believe the parts Chatman splits the narrative into resemble very closely those writers use in putting one together. So this book may actually help writers gain new insights into what they are doing instinctively.
First and foremost, however, it is a very useful book for the student and scholar of literature.