'Tau Zero' achieves a very difficult task. This is a 'Hard' sci-fi book that bases a story upon what could be some confusing scientific ideas. Time dilation and relativity are the key ideas that propel the story. Were they presented in a way that was superfluous to the story, or incomprehensible to the reader, the book would flounder. Instead, it soars.
The crux of the plot is simple. A 'generation ship' a vessel full of families that will take several generations to reach it's destination, is sent to establish a colony on a distant planet. During the journey, there's an accident, and the ship is left unable to reduce it's speed. As the vessel accelerates, the time outside the ship speeds by faster and faster, meaning that days, months and eventually years pass in what the helpless crew would perceive as meer seconds. Unable to stop or get off the ship, the protagonists hurtle towards the edge of the universe, and the end of time itself.
Tau Zero is a success because it balances characterisation, scientific concepts, and a compelling plot perfectly. The story is more than a show-case for clever intellectualism and the drama as the crew resolve a problem only to face something much greater is superbly written. Anderson expertly portrays the fear, hope, despair, ingenuity and even tedium experienced by the heroes on their eon-spanning journey as the story heads towards an amazing, but credible ending.
If there's anything bad to say about the book, it's the rather tepid scene-setting at the start. But once the ship is underway and the plot properly kicks in, it's an utterly thrilling, white-knuckle ride that's as smart as it is entertaining.
I read it one sitting during a night-shift at work, and, ironicaly, didn't realise where the time had gone. A superb story.