Teen urban fantasy is a popular sub-genre, and this first installment of a new series has all the essential elements. A city-dwelling teen discovers an invisible world of magical beings and monsters living hidden among us, and that she has a place and power within that world due to a past that has been kept hidden from her. It's the variations the author wrings out of the formula, and the attitude, that make the difference. Author Cassandra Clare doesn't go for the teen sarcasm and black humor (much), nor the hip urban cool, of some of the other members of this small but growing category.
Instead, she offers an intriguingly complex world with reams of backstory involving numerous characters, creatures, factions, and relationships. In addition to the various sides among the Shadowhunters, there are vampires, werewolves, faeries, warlocks, and others, each group with its own politics, powers, and agendas. Then she wraps it all up with exciting action told in vivid, occasionally melodramatic, but always engrossing, prose that sweeps the reader along and makes even the exposition fascinating.