The Unselfish Gene
The Unselfish Gene is a science fiction novel by Robert Burns, for which I was lucky enough to make the cover image. In the novel, humans on Earth are largely wiped out by a plague with only a few survivors left in a zombie-like state. Forunately a lunar colony survives, but, lacking the supply of materials from Earth, throws its resources into construction of the Anita, a 40,000 tonne Orion-drive spacecraft. It's a race against time (presumably - I haven't read the novel yet) for the colonists to reach Earth before a massive planet-killing comet comes along to finish the job. Well, how could I resist ?
You can buy the book here. I have no idea if it's any good, because I never did get my promised hard copy.