This XKCD sums the whole thing up perfectly:
“You know the scene in Apollo 13 where the guy says ‘We have to figure out how to connect this thing to this thing using this table full of parts or the astronauts will all die?’
The Martian is for people who wish the whole movie had just been more of that scene.”
Not sure I can do better than that. Ultimately, The Martian is a fun, light read with a whole bunch of interesting science mixed in. Weir’s writing style works really well for the portrayal of the main character (though other characters are a tad weaker). Overall: highly recommend.
Oh, and the movie is good too! But the book is better.