This is book 1 of the Infernal Devices series which is a prequel to the Mortal Instruments series.
Set about 100 years ago, we have the same types of characters (some are the same). There are ShadowHunters, vampires, warlocks and demons. The story seems more intense than the Mortal Instruments books though.
Even though the main characters are underage ShadowHunters (same) and there is the beginnings of a teen romance (same), it seems more intense because technology of the world is not the same and so the heroes seem more endangered.
The next book to be published within the two series is the second book of the Infernal Devices series. I'll be reading that and then contemplate the next Mortal Instruments book that is scheduled to be available this next spring.