I read the book a few months ago and absolutely loved it. It was World War Two... with zombies. The movie was nothing like it, but it was very entertaining. I was really disappointed there was no Battle of Yonkers though. It was important to show that the fully armed and prepared and stage US military could not stop the zombie threat.
I'm not sure how the next two movies will/would go from here. All the soldiers around the world will be immune to the zombies? Doesn't sound very fair just walking around gunning them down with no personal danger.