The book "A Forgotten Empire" was written by Robert Sewell and it focuses on the Vijayanagar Empire. This book provides insights into the history, culture, and administration of the Vijayanagar Empire, which was one of the most powerful empires in South India.

Option 1: The Kushan Empire is not the correct answer. The Kushan Empire was a Central Asian empire that existed from the 1st to 3rd centuries CE, and it had no connection to the Vijayanagar Empire.

Option 2: The Mauryan Empire is also not the correct answer. The Mauryan Empire was an ancient Indian empire that existed from the 4th to the 2nd century BCE, much earlier than the Vijayanagar Empire.

Option 3: This is the correct answer. The Vijayanagar Empire was a medieval South Indian empire that existed from the 14th to the 17th century CE. The empire was known for its architectural marvels and patronage of arts, and it played a crucial role in preserving Hindu culture and traditions in the face of Islamic invasions.

Option 4: The Mughal Empire is not the correct answer. The Mughal Empire was a powerful empire that ruled over large parts of