I have to agree, trying to fit a Sigma book into a movie would not work.
I am glad to see this though. I have been reading Rollins' books since he first started. Although I am glad he switched from standalones to the Sigma books. His standalones were very formulaic. I liked the formula, which is why I kept buying them, but the Sigma's are much better written. I guess that just comes with experience.
I look forward to the movie.