I did something similar yesterday; Annabel was down for the weekend and we wanted to see a film so Caroline and Annabel went to see Suffragette whilst I saw The Martian. Totally agree - absolutely brilliant film. As Steve says the special effects are outstanding but they completely complement the film. The author of the book the film is based on wrote an article about the book in last month's Stuff magazine and said he had lots of contacts with various scientists to make sure the science was as accurate as possible. Lots of geek references for those that like that sort of thing e.g. 'steely-eyed missile man'.