Book online before finishing it.

Space Center, 2015
Andy Weir, the son of a particle physicist and electrical engineer, has a background in computer science. He began writing the book in 2009, researching related material so that it would be as realistic as possible and based on existing technology.[8] Weir had previously used the concept of humans stranded on Mars in his webcomic Casey and Andy.[b] Weir studied orbital mechanics, astronomy, and the history of human spaceflight.[9] He said he knows the exact date of each day in the book.[10] He specifically avoided physically describing the characters when not necessary for the plot.[11]
Having been rebuffed by literary agents when trying to get prior books published, Weir decided to put the book online in serial format one chapter at a time for free at his website. At the request of fans, he made an Amazon Kindle version available at 99 cents (the minimum allowable price he could set).[8] The Kindle edition rose to the top of Amazon's list of best-selling science-fiction titles, selling 35,000 copies in three months, more than had been previously downloaded free.[8][10] This garnered the attention of publishers: Podium Publishing, an audiobook publisher, signed for the audiobook rights in January 2013. Weir sold the print rights to Crown in March 2013 for over US$100,000.[8]