I cannot praise Ant's lateral thinking enough. The story line is topical in that a bunch of disparate desperates put themselves in a nuclear fallout shelter, not unlike the TV big brother house. Much of the genius in the writing follows from the interactions between them and the chaos theoretical discoveries they make of hidden depths in the shelter.
Aspects of quantum physics are used effectively with respect to simultaneous existing 'worlds' within their new underground world. The characters are Over the top but real enough to be your neighbours - even the crazy Dwarfius.

This is a must read. Written cleverly and with a Douglas Adams humour, I'd recommend it to anyone who feels they ought to know their SF genre.