I struggled over rating this one. Because although I loved the idea of London Below, and the colourful characters than inhabit it, I don't know whether I was grabbed by the novel itself.
Neverwhere is the story of Richard Mayhew (who insisted on being Martin Freeman in my head), a businessman in London who, as it were, slips through the cracks into a city below London, inventively named "London Below", where Rat-speakers and Sewer Folk grab what they can and pale women in velvet stalk the tunnels.
So, yes, a hugely interesting world, and a gripping enough story - the usual questing-for-revenge through dire perils and dreadful danger. But I would have liked to see more of London Below, more of how people live down there, not just its deepest secrets and magics. And the denouement seemed a bit of a cop-out, too. Just letting Croup and Vandemar fall through the hole? And surely the key ought to have opened the door even if it was only a copy? And do Richard and Door ever get together?
But it was good enough to keep me interested, and I suppose that's all you can ask. Nice ending, too, if a little sudden.