He is best known for his first published novel, The Martian. He wrote the book to be as scientifically accurate as possible, and his writing included extensive research into orbital mechanics, conditions on the planet Mars, the history of manned spaceflight, and botany. Originally published as a free serial on his website, some readers requested he make it available on Amazon Kindle. First sold for 99cents, the novel made it to the Kindle bestsellers list.

Weir was then approached by a literary agent and sold the rights of the book to Crown Publishing Group. The print version (slightly edited from the original) of the novel debuted at #12 on The New York Times bestseller list. The Wall Street Journal called the novel “the best pure sci-fi novel in years”. It was made into a film starring Matt Damon and Jessica Chastain, which was released October2, 2015. In addition, Weir is also known for his novels Artemis (2017) and Project Hail Mary (2021), and the short story The Egg (2009).

On a personal note, he currently lives in Mountain View, California. He has stated that he is agnostic and considers himself to be a fiscally conservative, social liberal, and tries to keep his political views out of his writing.