I thought it gave a bit more background and examples of the 5 areas. It is a quick and easy read. If you are not religious, you can skip big parts where he gets a bit 'preachy'. I used it as a tool, but far from an all inclusive how to save a marriage book.
I would suggest getting it from the library or used.
PS - Look at Gottman books too. I found those more helpful for my relationships.