All Souls: A Family Story from Southie by Michael Patrick MacDonald for Peter Sullivan's backstory and things in Book Six. I found this nonfiction book a fair and informative account of what took place in the 1974 riot and description of Southie.
Generation Kill by Evan Wright. He was an embedded journalist in Iraq with a US Marine Corps Force Recon platoon. In this nonfiction book, you'll recognize some of the behaviors of Peter and Chris in Books 1 & 2.