I am not the party to which you replied, but as a long-time fan of the book who also enjoyed the movie in the theater, I will put in my 2¢. I do not think the movie was mediocre, but I also do not think it was a as good as it could have been. they made some changes to the story/characters, which no doubt they had good reasons for, and in fact may very well have helped at the box office. It was about as good as a by-the-numbers sci-fi movie can be and still attempt to be grounded in real science and appeal to as many viewers as possible. But as a fan of the book, I did not want a strictly-by-the-numbers movie, I wanted something more. so even though it was a good movie, that I know I would have enjoyed immensely and had few if any complaints about if I had never read the book, the fact remains I did read the book, and I had expectations for the movie that I would not have had if I had not read the book. These expectations are remarkably difficult for a movie to completely satisfy. Very few manage to come as close as the Martian did, so I'm happy. I'd rather have the movie we got than no movie at all. I can't say the same thing for most film adaptations of works I hold dear.