William Warner Sleator III was born on February 13, 1945, in Havre de Grace, Maryland. His father was engaged in ballistics research at Aberdeen Proving Ground, and his mother was a surgeon for the health service there. Before he was three years old, Sleator and his family moved to a suburb of St. Louis, where he grew up in a house filled with books. Music, especially the piano, was an important part of his life.

After attending grade and high school in St. Louis, Sleator went on to earn a bachelor's degree from Harvard University. Even though he did not like Harvard and generally thought of it as a waste of money, he engaged in many activities that were useful preparation for his later life: writing music for student films and plays, writing reviews for the Harvard Lampoon, and keeping a journal that ended up containing...