^Your argument would have merit if they hadn't bought the rights to the book before ever having an idea for the movie. nevermind a script. And I would argue that the movie we are getting is far enough from the book that even copyright laws wouldn't be an issue.
I'm sure Paramount saw the book and thought it may be a good story and bought the rights. The problem obviously has become is how to make the film into a blockbuster and adhere somewhat to the book and the original storyline.
made a good point earlier as well that it may have been an interesting story for some of us
to film the zombie plague as written, I'm doubting that approach would have had mass appeal. The general public expects big visuals and it to be fast paced.
I'll give you a great example of a big budget film that flopped but still IMO was a great story. I saw Cloud Atlas
last weekend. Great story, top rate actors, good story [albeit a little long at almost 3 hours] but very, very slow
. And it cost a fortune to film at nearly $100 million. It's being dubbed the $100 million flop.
World War Z is a great story as written but not IMO a great story to put into a ~ 2 hour film with big stars who command large salaries which makes the film very expensive to make and therefore demands a large audience to pay for itself.