The Martian "Watch"
is Mark Watney an astronaut left behind on Mars with meager resources.
He has to solve many problems of human survival on another world. He has to breathe air, but the atmosphere on Mars is very thin. He needs water, but accessible drinking water on Mars comes from biological processes he has to maintain. He needs food, enough to last until rescue arrives from Earth. Of course, Mars won't cooperate with plans and things go south, things explode and Mark Watney makes mistakes.
What strikes me about The Martian is they didn't turn this into a drama about science. Mark Watney dances around, the script is light and the relationship between NASA employees and the astronauts were down to earth. There were running jokes about mission commander's taste in music (disco) and the bull* is present in the conversation. I guess the astronauts weren't gods after all.
The movie didn't depart from the book by Peter Weir. All the science are intact even the NASA speak.The book has a lot of fans, me included.