How did Isaac Asimov manage to write or edit over 500 books in his lifetime?

The answer

Isaac Asimov (1920–1992) authored or edited over 500 books spanning science fiction, mystery, popular science, history, humor, religion, and literary criticism. His works appear in nine of the ten major Dewey Decimal categories. Asimov typed 90 words per minute on his IBM Selectric typewriter and routinely worked 12-hour days, seven days a week. He published his first story at age 18 in 1938 and never stopped. His most famous contributions include the Foundation series, the Robot series, and the Three Laws of Robotics, which have profoundly influenced real AI ethics discussions. He also wrote a guide to Shakespeare, annotated Paradise Lost, and published joke collections. At his peak, he released over 15 books per year.