Once again, this isn't the kind of book I normally read. Yeah, it's kind of science fiction and I do read some science fiction, but I've never read a book about the (relativity early) space program. That doesn't really work (since there have been no manned trips to Mars (just go with it, anyway), but most of the science fiction I've read has long distance space travel without a lot of drama. This is relativity short term space travel with massive drama.
I think this book has too much science in it. I understand the need for science, but I don't know anything about chemistry (I took a chem class in high school, but that's all I know and I've forgotten about most of it now). I'm not going to say I was lost, since it's not that hard to understand but there were points were I thought the plot was lost, buried under so much science.
That said, I really liked Mark and his strange, snarky humor. I'll admit that there were several points that I really didn't expect him to get off Mars at all (spoiler: he does but then that's pretty much the end of the book). He gets nearly blown up several times, mostly due to his own stupid ideas. Yeah, they work but really. Some of them I shook my head and told him (sometimes out load) that he was going to get himself killed. I think I would have been really mad if he had died before getting off Mars, but I really did expect it at some point. Now, they aren't back on Earth but they are on their way and I guess we're meant to assume they made it back okay.
I almost forgot. Mark makes a Star Trek joke fairly early on in the book. It's more a reference than a joke but I did a double take. "Damn it Jim, I'm a botanist not a chemist." Yeah, loved that!