While not as well known as some of his other
books, such as the
Polesotechnic League series,
Poul Anderson has said that The Boat of a Million Years is his best work.
The premise of the book is simple: It follows the lives of a group of immortals through the ages. While this has been done before, such as in Robert Heinlein's Time Enough for Love, this book is done in a slightly more 'hard scifi' style, and focuses more on the history of mankind.
Written in a short story style, the chapters focus on how the characters deal with their condition, and on how the world reacts to them. Where the novel shines is in its depiction of ancient history as a living, breathing entity. The different areas of the world seen truly are different. While in Europe the immortals, when discovered, are treated as evil, in the east, they can be accepted, in many ways. Some overlooked cultures are shown as well, such as Pre-European Native Americans, and ancient Scandinavia. Historical figures are downplayed, but they are present. One chapter has a conversation with Cardinal Richelieu, and another has two characters who figure in Norse legends, one being Nornagest, although probably only one familiar with the names, or the myth, will catch it.
The book winds up far in the future, when the 'Survivors', those immortals who managed to live to the modern age, leave Earth. It is at this point that Anderson expounds, through the characters, what it means to be truly human.
Part Historical, Part Sci-Fi Epic, this is one of Anderson's best.