You expect too much,
First off, the movie wasn't supposed to be the book. Did you notice how many times it was referenced? It was about the book.
And, considering one had to wear the glasses the entirte time, it was long enough. The 3D is goo but it still has some work to do as far as human interaction.
As for plot, well, it's a Brandon Frasier action/popcorn movie that was designed to provide a few laughs and 3D thrills, it's not trying to be great art.
It was fun and the 3D made it worth the price of admission, but I won't be buying the DVD.