Sita Ram Goel's Hindi classic "Shaktiputra Shivaji" is highly underrated. Its introduction is a masterpiece that rips apart Jawaharlal Nehru's pretence of being a historian.
This is the little-known story of a Jhain, a prosperous town in medieval Rajasthan, heartlessly obliterated by Jalal-ud-din Khalji. Now it is known as the Chhan village.
Jadunath Sarkar spent a fortune from his pocket for building a vast and invaluable personal library, which became the single-most hub for studying the medieval history of India.
A highly interesting compilation titled "Precis of Palace Intelligence" gives us an insider's picture of Bahadur Shah Zafar's Red Fort inhabited by 2000 people.