Here's the back-cover copy:
Twenty-seven years ago, Sam and Dean Winchester lost their mother to a mysterious and demonic supernatural force. In the years after, their father, John, taught them about the paranormal evil that lives in the dark corners and on the back roads of America... and he taught them how to kill it.
When renegade angel Castiel alerts Sam and Dean to a series of particularly brutal killings in San Francisco's Chinatown, they realize the Heart of the Dragon is back. John Winchester faced the terrifying spirit 20 years ago, and the Campbell family fought it 40 years ago--can the boys succeed where their parents and grandparents failed?
A brand-new Supernatural novel that reveals a previously unseen adventure for the Winchester brothers, from the hit CW series!