Welcome brother. Delving into controversial aspects is not the best way to learn some thing. So in deed you started on a wrong foot. But then life is like that. There is a long thread here on Sunni Forum about the matters relevant for you. I have a few books on Sunni-Shia matters but they are in Urdu and I do not know about the availability of their English translation. But again there are very knowledgeable brothers on this forum who'll help you out. Wassalam