I'm sorry to say I found this more or less unreadable. In theory, it's a book about radicalisation of Muslim youth (read, 'boys') and the strong bonds between siblings (read 'girls'). However, the basic premise seems to be a failure of parenting, which sends the brother of the title looking elsewhere for comfort. So it's a case of ACE (adverse childhood experiences), a cliche of social psychology and all too common in violent families. The structure is poor, with too many new characters introduced too late in the book, and the sister is a cringe-making combination of strength and cliched female self-abnegation.