Poul Anderson’s book Tau Zero stands out in the genre in large part because it does precisely the thing that one so rarely sees in science fiction: it takes a keen interest in the emotional lives of the characters in the novel, which the novel combines this with a general fascination for all things scientific. In Tau Zero, these two often competing themes in the genre work together with a synergy that makes the novel much more than just another deep space adventure story.
From practically the very first page, Tau Zero sets the scientific realities in dramatic tension with the very real emotional and psychological states of the travelers: you have the time factor and their emotional response to the consequence of traveling at this high rate of speed and the time that has passed. This tension is a dynamic that Anderson explores with great success over the course of the novel as fifty crew-members settle in for the long journey together. While they are a highly-trained team of scientists and researchers and therefore professionals, they are also a community of individuals, each of them trying to create for him or herself a life in a whole new space (or literally, in space).
It isn’t too long, however, before the voyage takes a turn for the worse. The ship passes through a small, uncharted cloud-like nebula that makes it impossible to decelerate the ship. The only hope rather, is to do the opposite and speed up. But acceleration towards and within the speed of light means that time outside the spaceship passes even more rapidly, sending the crew deeper into space and also, further into an unknown future.