The Boat of a Million Years
Poul Anderson follows a handful of people who simply do not die, from the Phoenician world through Roman Gaul, medieval Russia, the American frontier and on into an interstellar future. Each era is a self-contained novella before the immortals begin finding one another. The interest is less in why they are immortal, which Anderson barely explains, than in what outliving every attachment repeatedly does to a person. Published 1989 and among his most ambitious late books.