I am reading the second chapter and it is somewhat confusing. Many of the Sufi orders appear to be humanistic blends of Islam and regional religions. We have a stereotype of the Pagan as inhuman and uncouth. However, this is inaccurate and while human sacrifice
was a real phenomena it did not produce endless jihad or mindless genocide ala communism or Nazism.
The question of what is Islam will be decided by Muslims themselves. The question of originalist is not a Muslim question itself but is something that crosses denominations. The mess at the Anglican church is also largely originalists vs Marxist hacks. This is seen in Judaism with Modern Orthodox vs the reform and some of the reform movement is Marxist.