I recently read Gunsmithing Shotguns, it was a good read. Dont rember by whom but I got it at Amazon. I have a few other's at home, I'll attempt to get you a list when I get back there later this week.
Penn Foster Gunsmithing Student
Personal Arsenal: Mossberg 500 20ga combo; Baikal IZH-43 12ga; Western Auto 16ga Bolt Action, Marlin 597 .22LR