Tau Zero is a tremendous novel, justifiably regarded as a classic, that proves two important things right off the bat: that hard science novels don't have to be tedious nuts-and-bolts physics lectures, and that a book can run fewer than 200 pages and still be a true epic.
The story concerns the Leonora Christine, an exploratory vessel on its way to a distant world. Its crew knows that, by achieving speeds as close to that of light as is possible, Einsteinian relativity dictates that by the time they return home, all their friends and loved ones may well be old and grey, if not dead and gone. What they do not expect, however, is for their craft to collide with a young nebula. But that's exactly what happens, knocking out the craft's decelerators and throwing our intrepid heroes into literally the worst of all possible scenarios: no way to slow down, no way to stop, no way to go home, in fact nothing to do but keep going. At first, the will to survive at all costs rallies the crew. But inevitably, simple humanity sets in and assorted crises emerge, none of which is helped by the increasingly bad news that keeps coming from the bridge.
I'll confess to being a scientific layman, despite my fondness for hard SF. In fact, the one thing I appreciate best in a hard SF novel is its author's ability to make even the most advanced and complicated scientific concepts clear to me. In short, to educate as well as entertain me. Anderson explains the science behind his story with admirable clarity, no matter what his readers' level of scientific literacy may be. As the tale barrels on towards its truly spectacular climax, you feel the claustrophobia and tension aboard the Leonora Christine with a sweaty urgency. The interactions among the characters are consistently convincing. Even scenes that seem a bit soapy at first make you shrug and confess that in this sort of crisis, people may well indeed act this way.
One might gripe at the denouement, which may seem a little too good to be true given all our heroes have been through. But overall, there's no denying that Tau Zero is one hell of an exciting, breathless thrill-ride through the galaxies — and beyond.