His specialty was writing novels based on monetary trends and historical facts concerning complex matters of international finance. Despite the underlying complexity of his novels, his lucid writing style had enabled readers to learn complex concepts such as interest rate swaps, and his novels had often been bestsellers. The Billion Dollar Sure Thing (1973) received a 1974 Edgar Award from the Mystery Writers of America for Best First Novel, and the The Silver Bears (1974) was turned into a 1978 movie of the same name, starring Michael Caine.
Erdman also regularly wrote financial columns for www.marketwatch.com. He was a leading expert in the international economics field and has published non-fictional works, such as Tug of War, which set out his views on exchange rates and the international financial system.
Erdman was born in Ontario, Canada, to American parents. He graduated from Georgetown University’s Edmund A. Walsh School of Foreign Service. He received his PhD from the University of Basel. Erdman had resided in England and Switzerland. He maintained a Northern California residence since 1973 and lived in Healdsburg, California.
Erdman was not only a former Swiss banker but a former president of a Swiss bank. At one point he was imprisoned after the bank got involved in a currency speculation scandal. Several officers of his bank served prison terms, much to the surprise of American readers, who were unaccustomed to seeing corporate executives jailed for the activities of their companies. In television interviews, Erdman has observed that Swiss prisons had better food (he could have meals sent in by hotels and restaurants of his choice) but Swiss laws did apply to the "privileged classes" as well as to ordinary mortals.