This is so much better than I was expecting.
I picked it up just because it was by Adrian Tchaikovsky. If you read the summary or blurb, it doesn't actually sound all that interesting:
The Church of Armes of the Light has battled the forces of Darkness for as long as anyone can remember. The great prophecy has foretold that a band of misfits, led by a high priestess will defeat the Dark Lord Darvezian, armed with their wits, the blessing of the Light and an artifact stolen from the merciless Spider Queen.
So I was basically expecting fantasy quest blah blah...
But the book (or novella as it's marketed) starts off from a giant spider's point of view, one of the offspring of the said Spider Queen ("Mother") who gets sent along with our band of adventurers to show them their path. They find travelling with a giant spider objectionable, however, so their wizard turns him into a spider-like man, the poor thing, and he continues to be one of the point of view characters. So he's technically one of the forces of Darkness and he's travelling with these people who are obsessed with Light (alright, some of them are) who are probably just going to kill him after he helps them and don't consider him a person at all.
It it to Adrian Tchaikovsky's credit that he makes me sympathize with the spider character.