Hey no problem, a fellow cinephile here. And yes I knew it was on a book but did not read it. I liked the movie for a whole set of reasons (For instance, Christopher Walken's performance) but reading the book would definitely have affected how I value the director's work. I had a similar discussion with my uncle, who is a writer and director, about another movie: The Girl with the Dragon Tatoo (The original version, not the American adaptation). My uncle read the books; I didn't. I really liked the movie, and found the plot rather satisfying to some degree, but my uncle hated it, and said the director simplified things to an alarming extent, losing all the interesting details that made the books successful. So I think reading the books is a good habit if one wants to judge the director's intention, but sometimes I just don't have time.

Update: I reread your question, and I think you want to know if directors are taking too much credit which ought to go to the book writer? I think in this case we might disagree about the director's function, which I think goes far beyond the intricacies of the story.

Thanks for the reply.

As for the clarification, I was more concerned with people attributing the derivative work with the credit of the movie moreso than the director on the whole. I probably only phrased it how I did since you used Spielberg's name directly.

The thing I find irritating (on a grander scale, not pertaining to you, specifically) is when cases like this arise where the movie rides the success of the book.

I get that it's probably specific to people who have read the book vs. people who haven't, but I'm usually interested enough to ask, as sometimes there are cases when directors take the movie to a level the source material didn't, just as there are times when a director is unable to take good source material and turn it into a good movie.

Thanks again for the insight.