House of the Dragon is based on the book Fire & Blood by George R.R. Martin. This novel, published in 2018, serves as a historical account of House Targaryen, detailing their rise to power in Westeros. The series specifically focuses on the Targaryen civil war known as the Dance of the Dragons, which takes place about 200 years before the events of Game of Thrones. Fire & Blood provides the foundation for the show's characters, conflicts, and political intrigue, making it an essential read for fans who want to dive deeper into the history of Westeros.