Thomas Hegghammer (from Norway) has edited a book 'Jihadi Culture: The Art and Social Practices of Militant Islamists', published by Cambridge University Press. No reviews yet, but his past writings suggest worth a look.

A couple of passages:
Jihadists did a lot of things seemingly at odds with their brutal image: weeping, writing and reciting poetry, singing, recalling and interpreting dreams, perfecting their manners and taking an inordinate interest in their appearance.

(Militancy) is about more than bombs and doctrines. It is also about rituals, customs and dress codes. It is about music, films and storytelling. It is about sports, jokes, and food.....the culture underpinning Islamist militancy acts as a kind of gateway to the ideology, rather than vice versa.

I think that’s a very powerful narrative. And the culture is a glue that has kept lots of different groups together in the past and I see no reason why it shouldn’t in the future.
Link to the review:

In the UK soon available via: 'Jihadi Culture: The Art and Social Practices of Militant Islamists'

In the USA Amazon says available in September 2017:

This thread one day will join the main thread on radicalisation:Studies on radicalization & comments