As you know I can find many books on internet regarding any sect but can you please suggest some AUTHENTIC books of Shia school of thought regarding:1- fiqh 2-Marriage3-Ahadith of Muhammad (saww)4-Life of ahle bait5-About Imam mehdi (as)And you can suggest too if you believe that some book can help me.JazakALLAH.

Yes indeed I will compile a list but for now best website to visit is al-Islam.org and please go to the Sunni-Shia dialogue section