R.A. Montgomery, author and publisher of the beloved Choose Your Own Adventure children’s book, died on Sunday at age 78 at his home in Warren, Vt.

The cause of death was not disclosed in an announcement published on the Choose Your Own Adventure website.

Born Raymond Almiran Montgomery, he graduated from Williams College in 1958 and moved on to Yale Divinity School, where he was soon after kicked out for “spending too much time skiing and mountain climbing.” His first job was at The Wall Street Journal and after a short stint as an assistant dean at Columbia University, founded the Waitsfield Summer School in Vermont in 1966. There, he focused on children with learning disabilities.

He first started working in publishing in 1975, co-founding Vermont Crossroads Press with his then-wife, Constance Cappel. There, he published Ed Packard’s children’s book Sugarcane Island as the first in a series called The Adventures of You. Montgomery wrote the followup, Journey Under the Sea, under the pen name Robert Mountain. After selling the Vermont Crossroads Press to Cappel, he took the series with him to Bantam books, where it was rebranded as Choose Your Own Adventure, which went on to become the fourth bestselling children’s book series in the world.

He went on to write Choose Your Own Adventure books for nearly 40 years, with his most recent title, Gus vs. the Robot King, being released in September.

Montgomery is survived by his wife, son, Anson, daughter-in-law, and two granddaughters.