I really enjoyed reading this book and the main reason I loved it so much is Mark Watney. He's an incredibly funny and interesting character with a very positive mentality. He's the most important POV in the book and through his log entries we follow everything that happens on Mars. Very nicely written this way, but also very compelling. I really felt for the guy when reading. Another asset of the book are the great comments throughout the log entries; the book contains a a lot those that are worth remembering.
The story itself was great as well; I was really pulled into it from the start. I liked it much more than I would have thought from the beginning. The book however gets a bit technical at times, and it's something that could irk some people. I myself tried to understand most of it to a certain degree, and if I didn't, I just got along with it and in the end it didn't ruin any of my reading pleasure. Now that I've read the book I'm already looking forward on watching the movie.