OK have now (AT LAST) finished this book.
The narrator was very quirky, yes- quirky to say the least. I'm not sure I liked him or found him that engaging, to be honest, and I don't know- for me, if the narrator doesn't feel like an 'attractive' character that usually spoils the book to a large extent.
The atmosphere of the book (Scotland, winter, kind of noir) was very convincing yes. I thought that was the strongest element in the book.
As for the storyline itself, it didn't convince me as much. I was fascinated at the beginning & loved 'getting into' the book, but gradually it felt like it was dragging on somewhat. The narrator kept going around & talking to all sorts of people about the (possible) crime & I thought after a certain point the novel became about these encounters rather than about the crime. It would have been much more successful, I think, if the characters with whom the narrator engaged were different, but each felt more seedy than the one before.
So all in all, even though I respected the author's writing style & talent, this book didn't 'do' it for me, but as I said it's probably because I didn't find the characters attractive & engaging.