I almost didn't read the book, because I disliked the movie, but I am so thankful I did. As a Wikipedia addict, The Martian, to me, felt like reading a 369 pages long Wikipedia entry whose content was entered by a really witty and funny man. The technical explanation of how and why things work, specially on Mars, was riveting. I loved how Andy Weir managed to keep the plot thrilling and interesting, despite getting really technical at places.
I also loved how Mark Watney ended his log entries with a very beautiful quote on humanity. He should be non-fictitious!
Given that The Martian was his debut novel and a finished product of his mere passion for space science, Andy Weir is one of my biggest inspiration as a writer.