A long-time resident of Santa Fe, New Mexico, Hamilton was a skilled outdoorsman and hunter who wrote non-fiction articles for outdoor magazines and published a book-length collection of them. For a number of years after leaving Santa Fe he lived on his own yacht, then moved to Sweden, where he lived until his death in 2006. A number of his Matt Helm novels are situated in the Santa Fe area and American Southwest in general; as Hamilton developed an interest in boating, many of the books began to have a nautical component as well.