The progressive disappearance of ijtihad, personal interpretation, in favor of the study of sharia, pretty much ended the prominence of Arab civilisation by the 14th century. The deadly clash between Sunni and Shi'a, not mention Sufi Islam, continues as well. Among these, there are many variants. The currents that want to return everything to the way they were in the 7th century are the ones making some Muslims ignorant on purpose. Otherwise, some of the very best human beings I know and value as friends are Muslim.

I will pass on Dutton's book... thanks for letting me know it's not worth anyone's time.