Reddit reviews Aftermath: Following the Bloodshed of America's Wars in the Muslim World

Patrick Cockburn has a book on Muqtada Al Sadr that covers alot of these topics. Muqtada Al Sadr, the Shia Revival, and the Struggle for Iraq. Muqtada's family was one of the most prominent backers of the new Shia empowerment train of thought. His father Ayatollah Sadeq al Sadr known as "The White Lion" opposed Saddam Hussein and was assasinated. While his uncle was Musa Al Sadr from Lebanon whom Hezbollah consider their spiritual leader even though he went missing on a trip to Libya. So Muqtada has always been involved with "the Shia revival" movement.

Also recommend Nir Rosen's book Aftermath. Nir Rosen is a New Yorker of Kurdish origin, who basically moved to Baghdad after the 2003 war and lived there for 4-5 years. Haven't read his first book yet, but this one really goes into detail on the spread of sectarianism. The first half covering the Iraq civil war on the ground, and the second half of the book he travels to Egypt, Lebanon, Jordan to witness the fallout. Basically how thousands of wannabe Jihadists went to Iraq to fight the Americans, got radicalised, then went home to Lebanon, Egypt, Jordan with these sectarian views and began organising.

Finally the book that thought me more about the Middle East than any other is Robert Fisk's The Great War for Civilisation its around 1,500 pages long but covers all the major events from the 70's onwards in the Middle East from a journalist who has spent 30 years living in Beirut. It's more a general history than specifically dealing with sectarianism but highly recomended.