Gebler was born in Dublin, the elder son of the Irish writers Ernest Gebler and Edna O'Brien. He is a novelist, biographer, playwright and teacher, frequently working with prisoners in Northern Irish jails. His novel The Dead Eight, based on events that took place in rural Tipperary in 1940, was described by Julian Evans as having a "Swiftian understanding of the world's secret machinations". His other novels include How to Murder a Man (1998) and A Good Day For A Dog. Driving through Cuba: An East-West Journey was published in 1988, and his other non fiction books include The Glass Curtain, about the sectarian divisions of Belfast, and Father and I: a Memoir, a book about his difficult relationship with his distant father.