I had no damn idea:
1) It was originally self-published
2) It was originally a serial
3) It was once free
Andy Weir and his book ‘The Martian’ may have saved NASA and the entire space program
The story unfolded as a serial over the course of several years. At the request of fans, Weir repackaged it in an e-reader version. Some readers struggled with the downloading process, so Weir then put it on sale at Amazon via Kindle Direct Publishing, charging the required minimum of 99 cents per copy. More people downloaded it at that price than had ever downloaded it for free. They gave it positive reviews.
Not a single damn person in my bookish Twitterstream ever mentioned it to me.
And you would think Amazon would have pimped the shit out of it. They fell down on this job!
Podcast page: How Andy Weir Took ‘The Martian’ From Blog to Bestseller to Blockbuster Movie (Starring Matt Damon)
— thanks to @JulietaLionetti
Mike Cane’s xBlog 
Just this week I listened to Jonathan Strahan and Gary Wolfe review The Martian on The Coode Street Podcast. They discussed the book (and it’s failings), but I don’t think they mentioned that it was originally self-published. Or if they did I missed that bit.
They were not kind to the book though. The phrase “iron characters and wooden prose” sticks in my head. However, despite the criticism I think it’s hard to argue that the book has not been successful, wooden prose notwithstanding. That’s even more impressive after learning that the author struggled to get it published.
If you listen to the podcast linked in the post, the writer admits his characters aren’t deep and none undergo any change. I’d still like to know if he ever heard of Robinson Crusoe on Mars.
https://en.wikipedia.org/wiki/Robinson_Crusoe_on_Mars
Will listen when I can. I did not know about Robinson Crusoe on Mars either! Actually, I’m surprised Strahan and Wolfe didn’t mention it.
Maybe they’re not old enough. *snort* I saw it in the theater back when.