Mark Watney, a wise-cracking mechanical engineer/botanist, is the seventeenth human to set foot on Mars, and the sixth member of the Ares 3 crew to step down from their Mars Descent Vehicle. But when he is left behind for dead in the hasty recall of the mission, he begins chalking up a long series of firsts.
However, this novel is not a science-fiction story, any more than Daniel Defoe's Robinson Crusoe was a sailing story. Watney's perilous position on Mars is more reminiscent of Jim Lovell's in Lost Moon. While he seems to be alone, he has NASA Mission Command, JPL, and multiple other agencies working to bring him home.
Once they realize he has survived, that is.
I got my undergrad degree at the University of Chicago. Half the people who studied botany were hippies who thought they could return to some natural world system. ... They spent most of their time working out better ways to grow pot.
There are any number of plot gimmicks in the novel, starting with Watney himself having the personality and knowledge to survive and stay sane in isolation on Mars. He just happens to have a number of potatoes that were not sterilized and flash-frozen, available to eke out his rations.
We don't care, though, because the story becomes a MacGyver-like trip through surviving in extreme circumstances. As David Brin put it, it is competence porn.
This frigid desert has been my home for a year and a half. ... I’ve done a little of everything here, because I’m the only one around to do it.
It isn't only Watney who displays extreme competence and inventiveness. For example, there is the "glorified Fotomat attendant" Mindy Sue who discovers Watney is still alive, when she notices in her satellite imagery that things have been moved at the "abandoned" mission site. Rich Purnell is responsible for calculating orbital course dynamics. In the end, his lateral thinking supplies the answer to the problem of getting Watney home before his food runs out.
Most impressive, though, is the way that the space programs across the globe kick in with the resources to rescue this one man. Because Spock was ultimately wrong, and Kirk was right:
Because the needs of the one... outweigh the needs of the many.