Charles Darwin
Originally published in 1859, On the Origin of Species is one of the most important texts ever released. Written by the father of evolutionary theory, Charles Darwin, it not only restructured how we view life on Earth, but also provided an important step in our ability to answer the big questions: namely, 'where did we come from?' Taking over 20 years to write, Darwin considered the finished manuscript to be about half the length he initially intended. He 'rushed' toward the end, due to the similar work of Alfred Russell Wallace which was also due to be released, even limiting the time grieving for the death of his son to 5 days. The work itself is now one of the most famous in history, arguably contributing more to scientific and rationalist thought than any other singular release.