The Shadowhunters: Eleven books as a trilogy, a pair of trilogies, and two story collections.
Author: Cassandra Clare
Nutshell: Demons exist. So do a secret race of demon-slayers. They are called the Nephilim, or Shadowhunters.
In the late 2000s, Clary Fray discovers them in New York city, and learns that she is one of them. Her mother not only raised her as a normal human but erased all her memories of the magical world. But now Clary has discovered her birthright, and just in time, as she is about to be a key player in a war between the Shadowhunters and their greatest shame: the twisted Valentine.
In the 1850s, Teresa Gray arrives in London, the city with all the best novels. She’s eager to meet her brother and start a new life after the deaths of their parents, but something’s not right. The women that pick Teresa up at the docks are, frankly, hideous and terrifying, and the place they take Teresa is more like a prison than a home. Then they torture her, forcing her to perform dark magic. But one night, the Shadowhunters raid the place, expecting a den of demons. Teresa is at least as suprised to find a rescuer breaking into her room as the rescuer, one Will Herondale, is to see her there. After a slight misunderstanding (in which Teresa proves quite able to defend her virtue from mysterious young men at midnight) Will manages to hold her off long enough to rescue her, and takes her back with him. This is fortunate, as Teresa has the first warning of one of the greatest threats the Shadowhunters have ever faced.
In the Bane Chronicles, Magnus Bane, reprobate warlock, makes his irreverent, immortal way through the centuries, loving deeply, living wildly, and learning, but not too much. Too much learning is for people who want to be serious. And depressing. Magnus Bane is never serious or depressing. If he starts to show signs of seriousness, he gets himself riotously drunk instead.
And in the Tales from the Shadowhunters Academy, Simon Lewis does some things because of spoilers from the previous books and then some other spoilers happen and then more spoilers.
Read-alikes: There are lots of “Turns out you’re actually a character in a fantasy novel” books like the Mortal Instruments. Try the Iron King, by Julie Kagawa, or the Tryll series by Amanda Hocking. For the Infernal Devices, I find The Girl in the Steel Corset by Kady Cross is satisfyingly similar. Any Buffy the Vampire Slayer literature is going to be like this also, though I haven’t read any myself.