Samuel Delaney famously said that SF made metaphors concrete ('his world fell to pieces'). In a recent online review of Counting Heads by David Marusek immortalradical praised an SF book for getting away from the merely metaphorical. Which, I get the point.
On the other hand, the Snow is (in my opinion) all about the metaphor. All the things that can be meant by Snow, by Snow Job, by White-out, by Cover-Up. Cocaine, Caucasian, even Tippex (Sno-Pake?) the use of which is indicated liberally in the text thus [blank].
Another notable fact about this book is that the main character is a woman in her thirties, a (very youthful) grandmother, part of the British ethnic group called Ugandan-Asian. I haven't read many novels centred on someone like this, very few written by men. She is a lively and very likeable p.o.v. character who makes some very big mistakes.
The book is in three parts.
The first part surely had its origin in those SF daydreams we all have (don't we?). What if it didn't stop snowing? What if that was how the world ended? It's almost a cosy thought, and what does that tell us about death?
The second part is a very Adam Roberts section. It's about politics and lies and social control and rebellion. A bit like his first novel 'Salt'. There are some interesting characters in this, most of all an insane writer.
The third part more or less thought-bombs the two previous parts. It's a fantasy section, which rewrites retrospectively everything that has gone before, with a few knowing refs to other SF novels.
For me the biggest emotional jolt was when we discover that an estrangement between a married couple is (probably) down to a terrible misunderstanding, which the reader has completely gone along with from the first moment. Foolish pride. I think this really happens between people. I know it happens between me and H (not to the same long term effect of course) and what a shame it is.