Riddley Walker - Russell Hoban - it's completely brilliant. Every other postapocalyptic thing I've read/seen pales in comparison; because it's not at all another of those po-faced meditations on how horrible human beings are, how civilisation is but a paperthin veneer and we're all cannibals at heart, etc etc etc. It's a genuinely strange, almost hallucinatory, sort of road trip through your own head; the writing is astonishing, experimental and woozy and weird. The setting in Kent makes it of special interest to urbs; the inevitable holes in the world-building and the lapses in logic just don't matter. There are horrors and mysteries and plenty of death but oddly it's not a miserable book; rather a thing of wonder. READ THIS BOOK. It is so worth it.
Marks out of ten would be wrong - about 20? 50? 1,000? Just read it.