theBearJewSaw it the other day. I thought it was really good. A few good reads on how the author of the book needed to adapt the story to make it work for the big screen.
One was about GoPro and how the book read that he narrated most of it, in a book that works, but in a movie its odd. So he added GoPro's for Watney to talk to. It ended up turning the GoPro into what Wilson was to Tom Hanks in Cast away.
Also the author wanted to keep it very scientific but knew decided to take the liberty of suspending science for the storm that blew away Watney. Because gravity is so different on Mars a storm that is 100 MPH would feel like barely anything. He wanted to do this because it sets the story to be Mars against Watney.
One really small detail that i noticed is that whenever they showed the sunset the sky would start to get even more red. On mars, instead of the sky turning that orange red like it does on Earth, it starts to turn a bluish color.
I thought the movie was great. Would definitely go see again.