It might have been a YA one. It was about a girl who lived with her gran having to be suddenly sent to stay with her mother who lived in a squat. She befriended a teen boy who also lived at the squat, and they solved some kind of mystery involving her dad and the IRA (?!). There was some mystery about yellow plastic explosive running through the book, with it appearing and disappearing; at one point the explosive was used to weight a large papier mache wolf mask.