In 1990, Gumbel took over the running of the Alpha Course that had been running there since 1977. The course was transformed under his leadership from being one designed for new Christians to one primarily for those outside the church who would not consider themselves as Christians. Gumbel serves as the public face of the course, being described by James Heard as something of a "Weberian charismatic leader". Gumbel is the author of a number of books related to the Alpha Course, including "Questions of Life" which has sold over 1,000,000 copies. Voted "Christian Book of the Year" in 1994, it has been published in 48 languages. Other related books include "Why Jesus", "Searching Issues", "Telling Others", "A Life Worth Living", "Challenging Lifestyle", "Heart of Revival", and "30 Days".