Thank you. Were there any specific triggers that helped it to become so successful in the region? I'm sure I'm asking for a simple answer to a complex question, so no problem if the answer is 'no'!

Before Islam what religion were the countries that we'd now consider traditionally Muslim (for example Iran, Iraq, Saudi Arabia, Afghanistan).

I'm aware that those countries didn't exist in the same form so I'm interested in the people who lived in those areas.

Are there any good (ideally not too heavy) reads about the early history of Islam? I find the spread of belief systems very interesting and enjoyed studying the history of Christianity many years ago.