I was pleased and surprised to encounter a copy of Poul Anderson's "Tau Zero" at the American Book Center when stocking up on books for a recent trip. This is one of a shrinking handful of books I still haven't read in the Gollancz Sci-fi Masterworks series, and I was happy to have found it.
"Tau Zero" is a novel about relativity, about a generation of astronauts who travel close to the speed of light, reaching other worlds in a few years subjective time (the rate at which people on the ship age), but several decades objective time (the rate at which the Earth they leave behind ages). In "Tau Zero", the idea of traveling close to the speed of light is the main character, and it is explored to the fullest, and with the highest respect for the hard science behind the concept. The technology behind their travel is roughly the same kind of ramjet that the main character in "World Out of Time" uses to circle the universe at relativistic speeds and thus outlive the society that imprisons him, but here it's not just a means to roll the clocks forward on Earth and encounter a new world.
The 50 astronauts (and potential colonists) in the ship which is the focus of the story must live together for years before reaching their goal and either founding a colony or deciding to brave the trip back home. Many of them have skills that are more useful when they arrive, and must find ways to occupy themselves. Even those of the crew who are busy with its day-to-day maintenance must find ways to keep their spirits up over the long haul even if the mission goes exactly as planned. Of course the mission does not go as planned, and Reynoud (arguably the main character) must play father to the crew and enforce the basic routines that help keep everyone's sanity as things unravel further and further. I won't spoil the ending except to say that it reminds me of the ending of Cities in Flight in its scope, but is more hopeful and amazing.
I enjoyed the book as a whole. It's hard sci-fi (with real science rather than science as magic) at its best, playing with the best science available at the time to see how it might change the human condition. I also think the drama is handled well enough. The only small thing that bugs me about "Tau Zero" are the characters. As in his "HeeChee" saga, Anderson can't resist the urge to analyze the characters, and adding that to the somewhat stiff way the characters tend to express themselves, the novel on balance feels a bit more firmly an intellectual novel than an emotional one. The same could be said of many science fiction works, and this is definitely one of the better ones. Highly recommended.