Mark Watney is part of a manned exploration team that's scheduled to study Mars for thirty days. A sudden dust storm forces the team to abandon the planet on Day 6 but - due to a freak accident - Mark is believed to be dead and left behind. The book is composed largely of a series of log entries in which Mark records his day to day activities, his goal being to survive on the planet until the next exploration team arrives in four years. Of course Mark needs food, shelter, oxygen, water, power, and so on.
Mark does have access to a habitable module, a couple of rovers, and various other equipment - and being a botanist, engineer, and extremely clever guy - is able to jury rig a lot of stuff to help himself. There's a ton of technical jargon in the book and numeorus scientific explanations of how things work (the author has clearly done his research). Eventually, after great effort and a daring journey, Mark is even able to rig up a communication system to talk to Earth. The book includes what's going on at Mission Control in Houston as well as a peek at Mark's crewmates that are returning to Earth.
If I was in Mark's situation I'd probably sit down and cry, but Mark is an optimist with a great sense of humor - and even though everything that can go wrong does go wrong - he's never down for long. Luckily Mark has some entertainment (music, TV shows, books) brought along by his former crewmates and his comments about some of this stuff (Disco, 1970s television series) adds humor to the book.
The story is suspenseful and engaging, and the characters are relatable and interesting. I liked the book and recommend it - especially to people who enjoy science and like to know how things work.