I thought about this some more, since I think I normally wouldn't like reluctant protagonists either. I relate easily to Garret because I can see why he's so conflicted. He's torn between family duty to give his sick and not-entirely rational mother some peace, his own opinion that the expedition is pointless, and his justified hatred for his brother. He feels stuck in a job he doesn't want.
He's also a walking, furry, deadly weapon, and everyone knows it. Despite his timid nature, even much larger animals regard him as a physical equal and see him as the obvious go-to for the very confrontations he hates so much.
I think the author did an especially good job of using hints and cryptic flashbacks to show why Garret is the way he is. He's seething with repressed rage. He's visibly and lastingly maimed by the same person he's risking his life to follow, for the sake of what sounds like a dysfunctional family relationship. He's more scared of himself than anything.
This is a setup for a really intense character arc, so I think you still might want to keep an eye on the updates.