City of Heavenly Fire is the sixth and final book in The Mortal Instruments series. Cassandra Clare has created a world in which supernatural creatures, magic, and humans coexist. Not an unusual theme these days, especially for a young adult book. The twist in this series is the addition of shadowhunters—humans who have angel blood in their veins and whose mission in life is to keep demons and other supernatural creatures from harming mundane humans. The books follow the adventures, tragedies, dramas, and triumphs of several teens—shadowhunters, humans, and others.
The story continues, or begins, in the prequel series Infernal Devices. And if you just can’t get enough about the shadowhunters, Clare is starting a new series, The Dark Artifices, which picks up where City of Heavenly Fire ends.