Limitless Book review

I didn’t realize that the new movie (Limitless) was based off a book I had already read and reviewed, The Dark Fields (my review) by Alan Glynn. Now, the book and the movie are very different stories (as discussed by Alan Glynn and screenwriter Leslie Dixon(writer on Hairspray, The Thomas Crown Affair and Mrs. Doubtfire) on IO9), so I am sort of curious how big the changes are.