Bussard ramjet accelerates it towards light speed allowing it, through time dilation, to reach across the 30 light year journey in just a few years from the perspective of the crew. Chosen for their ability to both crew the ship and colonise the Earth-like planet discovered in the faraway system, the 25 women and 25 men aboard the Leonora Christine expect never to see the Earth again, but busy themselves with science and learning, and also with shipboard romances.
However, while the ship is still accelerating, it passes through a wandering nebula critically damaging its systems for deceleration. Initially shocked that the ship is still accelerating and that their original target is now completely unattainable, the crew rally around a plan to continue accelerating out of the Milky Way and to repair the damaged systems in intergalactic space, before decelerating into a new system. But on exiting the galaxy, the Leonora Christine finds the "empty" space still too rich in matter to safely switch off the ramjet, so the crew decide to press on, increasing the ship's speed and further dilating time. The setbacks continue, and before long the crew begin to fray as there appears to be no end in sight to their journey, and the passage of time exceeds the lifespan of Earth's solar system. Worse, the universe around the ship is changing, and the astronomers aboard belatedly realise that the Big Crunch is underway ...
This is one of those books that's better in theory than it is in practise. The set-up is great, and a really neat exercise in special relativity, but the execution is very patchy, and the novel is quite dull for long stretches. Largely, and perhaps unsurprisingly, because the characters don't quite work on the page. Much like the physics in the story, they appear something of an intellectual exercise, with personalities that serve primarily to just bump the plot along - not a good way to imbue a novel with human interest. To be fair, Anderson does well setting up a very existential dilemma for the crew (press on and simply hope for the best, or destroy the ship and end the journey with dignity and sanity), one that's interesting to ponder outside the novel, but one that's not nearly as satisfying within it.
All that said, it was still well worth reading. For all its flaws in characterisation, it never descended to the sexist farce of certain other "classic" novels. Sure, it wasn't really quite up to the giants of the era, but its good bits more than balanced out its more tedious sections. I particularly liked how, as the ship approaches light speed and "tau zero", the universe becomes akin to regularly-spaced speed bumps, as galaxy after galaxy are sped through in subjective seconds, and serve only to feed the maw of the ramjet. And while the physics at the end is now very much out of vogue, I still rather liked how Anderson concludes the journey of the Leonora Christine. In part, probably, because said eschatology still seems somewhat more satisfying than the more probable alternatives.
Overall, I won't be rushing out to raid Anderson's back catalogue, but I'm pleased to have finally knocked this "classic" off.