I've never read the book so I didn't have a reference frame. That's probably why I enjoyed the film.
I watched the movie first before reading the book. When I saw it I felt "meh, not that good". I love the zombie genre and don't expect it to be Oscar worthy in order to be entertained, but WW Z just lacked something. When I had read the book. OMG. The book was awesome, and then I was really disappointed because had they actually tried to stick a little bit more to the book and it's content, the movie would've been a trillions time more epic. Instead they were just influenced by a couple of pages in the book and labelled it "WWZ" to get more attention. It's a pity