Literary agent, publisher, and author William Gladstone died on December 27 at his home in Cardiff, Calif. He was 74.

Gladstone’s publishing career began in 1978, when he joined the family-owned Arco Publishing Company. Following the sale of Arco to Prentice Hall, Gladstone ran the San Diego office of Harcourt Brace Jovanovich before opening Waterside Productions in 1982.

Originally started as a traditional literary agency, Waterside added a publishing division, production capabilities, and online courses. Gladstone is estimated to have completed deals for more than 5,000 titles, and had a hand in starting the For Dummies series by selling the first five books in the series, which were written by Dan Gookin, to IDG. Other authors he represented included Marie Kondo and Neale Donald Walsch.

As an author, the books he wrote included The Golden Motorcycle Gang and Be the Deal, both cowritten with his friend Jack Canfield.

In a statement, Gayle Gladstone, Waterside publisher and Gladstone’s widow, said: “Waterside is an extraordinary team of like-minded professionals who have been together for decades and are positioned to continue my husband’s legacy in helping publishers and authors make a better world."