It's been so many years since I first read City of Bones and everything that comes after that. But it's always fun to return to the shadowhunters world. In this case, I would definitely recommend reading Blackthorn Hall after finishing the other series because it definitely contains some spoilers. Overall, it's a nice addition for fans of the characters, full of little easter eggs and beautiful illustrations. The perfect book to read while waiting for the Last King of Faerie.