It is my opinion that the book version and the movie version of "An Occurrence at Owl Creek Bridge" are almost identical with a few minor differences. Both versions contained the same plot - a man standing on the bridge, about to be hanged and foreseeing what the outcome would be if the rope broke as he is dangling in the air. The book gives a lot of detail so that the reader can almost depict the "occurrence." In watching the movie, the reader can relate, in many ways, to what the author is writing about in the book. At first, the book was a little confusing to me; however, after seeing the movie and then re-reading the book, the story became much clearer.
There were a few differences between the two versions. One major difference in the movie is that there are no words spoken. Without reading the book one might not know what is going on in the plot. One would also not know why the man is standing on the bridge about to be hanged, where the story takes place, or when. Also one would not know who the lady is at the end of the movie. By reading the book version this can all be solved because the book version describes all of these aspects in great detail. Another difference that came to mind was the part in the book when the soldier approached Farquhar's house and asked for a drink of water. This section was omitted in the movie version of the story.
My preference, if given a choice, is to watch a movie version rather than read the book version. Visual effects usually make a lasting impression in my mind and help me to understand the plot of a story a lot better.