Salam.. MashaAllah..
Did you study the biography of Prophet Muhammad well?
Anyway, I want to suggest a few books on history of islam especially on Prophet Muhammad (pbuh&hp) and the history later, from both shia and sunni muslim historians and non-muslims as well..
The First Muslim: The Story of Muhammad by Lesley Hazleton (Agnostic Writer as she desribes herself)
After the Prophet: The Epic Story of the Shia-Sunni Split by Lesley Hazleton
The Message by Ja'far Subhani (Shia Muslim Writer)
Seal of the Prophets and His Message by Mujtaba Musavi Lari (Shia Muslim Writer)
Mohammad; Man of Allah by Seyyed Hossein Nasr (Shia Muslim Writer)
Polarization Around the Character of Ali ibn Abi Talib by Murtada Mutahhari (Shia Muslim Writer)
Hussain, the Savior of Islam by Mir Ahmed Ali (Shia Muslim Writer)
The Visage of Prophet Mohammad by Dr Ali Shariati (Shia Muslim Writer)
History of Islam by Mahdi Pishvai (Shia Muslim Writer)
Fiqh al Sirah - Muhammad Sa'id Ramadan Al-Bouti (Sunni Muslim Writer)
History of Islam by Mustafa Asım Köksal (Sunni Muslim Writer)
Biorgaphies of Khulafah Rashidin by Syed Qotb (Sunni Muslim Writer)
the first two and the last three is a bit against shia islamic history.. but, I like them anyway.. I have many more but these are good as a start
none of these are extreme in any way.. so, they might introduce the Last Prophet of Islam (pbuh&hp) and also his succession better.. There are sites you can get them as hard copy or if you like reading online books or would like to print some, I have most of them as e-books and I can share.. Please let me know.. thanks.. ma salam