If you are interested in the beginnings of Islam (i.e., the first 100 years) a book by Fred Donner, Muhammad and the Believers provides insights I have never read about before. In the beginning of the movement, the adherents were called Believers and referred to themselves and their compatriots that way. Christian and Jews were welcomed even if they retained their beliefs and rituals, and many occupied high ranking positions among the Believers. The rapid expansion was not fueled, at least initially, to conquer territory or plunder other peoples, but to expand the number of people who heard and adopted the rules that Muhammad received from God. They were doing this because (as was true in many parts of the Mid East in those years), the prophet believed that the Day of Judgment was going to come before he died, and he wanted to be able to meet God and say -- here is a large group of people who are following your laws as you commanded me to tell the world about.
It's a short book and doesn't reflect on present day issues except tangentially. It's fascinating