Mark Watney was struck by a sandstorm, impaled by a satellite antenna and stranded on Mars with no way to get off, and yet he still managed to find a way to escape the barren wasteland.
The biggest them that you can see from this book is that of persevering until the end. You can see that from when the HAB blew up. (Weir,139) Even though it seemed like all hope was lost Mark managed to fix the situation by salvaging what he had left. Later on, Mark is just about to get to where he has his only chance to escape Mars his rover ends up tipping over he somehow manages to fix the situation although it seems almost impossible to do so. (281)
Another theme of the Martian is isolation. Isolation is one of the biggest themes well because Mark Watney is stuck on Mars all alone (5). We watch as this brave botanist braves the rugged and barren planet. All alone until he manages to establish communications with NASA. The theme of isolation further extends itself when Mark is saying that he is the king and sole ruler of mars.
In conclusion, the two themes of The Martian, perseverance, and isolation. Help set and pave the way for the story unfold, overall I think Andy Weir uses those two themes to their full extent and that The Martian is a great read.