A good summary for what I think about the book is best explained by a few status updates I made while reading the book:
Page 8: "Lots of telling, not much showing. An inauspicious start."
Page 67: "So far, this reads like a Facebook chat. A very technical Facebook chat, but a Facebook chat nonetheless."
Page 216: "HOLY CRAP it's hard to stop reading this. What happened?"
Now, keep in mind that somewhere between page 67 and 216, I had a moment where I thought I was going to be abandoning the book because I had so many issues with the writing. It wasn't until I looked up and wondered where all the time had gone that I realized maybe there was more to this story than I first gave it credit.
There's no denying that the book is very poorly written. Aside from the telling, the structure of the book was questionable. The book opens with a scene where the main character, Watney, has been hit with flying debris on the surface of Mars, and he's left to consider the fact that his crew has abandoned him there, thinking he was dead. This is all told from Watney's perspective, and it worked well enough, but later in the book, we see the exact same scene, only this time from someone else's perspective. I wondered why the author didn't just open the book with that version of the scene, and then seguing into it from Watney's perspective. Since the second version of that scene didn't open with anyone reminiscing or dreaming of said event -- it just opened cold on that one scene and then led into the present day directly afterward -- it was a little jarring.
The story is also told through the main character's audio journal (mostly, but I'll come back to that in a moment), which detracted from the tension of the events. One entry would describe the next hardship in Watney's survival (and there were a lot, believe me), and then end with him saying, basically, "This just might kill me, but it's worth a try; wish me luck!" and then the next entry beginning, "Well, it didn't kill me," and then he would describe how it didn't kill him. I thought that it would have worked better to have the journal entry describe his mindset and state of survival, then jump to a third-person perspective of the events happening, and then jump back to Watney's journal. It wasn't just that the author was sticking to the journal-only narrative (several other viewpoints jump into the story as it progresses, including one that isn't even connected to a character), so I question why it was structured the way it was. Some of the better writing was in those other viewpoints, despite the fact that the secondary characters in the book were all stereotypes and cliches.
The whole book felt very amateurish, and I wasn't surprised when I found out later that the book had originally been self-published as an ebook. What few books I've read that were self-published ebooks (with very rare exceptions) wound up feeling amateurish, or at least like they needed an editor's hand to guide the author.
All that being said, though, the story is compelling, if only because you want to see what happens next to ensure Watney's survival. It moves along at a great clip, and keeps the reader engaged. There were a couple of times when I was looking for whatever spare time I had to read the next few chapters. I bought the book from a local seller, who was offering a money-back guarantee, and early on, I thought I was going to be taking her up on that offer. I was pleasantly surprised with how the book turned out, even after having my expectations set so high, and then fall at the beginning of the book.
I'd recommend this to anyone who likes survival stories and/or science fiction (we haven't landed anyone on Mars yet), but with the caveat that the writing may be something you'll have to overcome. If you were able to overlook Dan Brown's writing to enjoy his stories, though, don't hesitate. Start reading this now.