Dark Goddess by Sarwat Chadda
This was amazing. You absolutely have to read the first one first - it's referred to often in this book, part of Billi's personal growth depends on events in the first book. It's nicely done, but you may find yourself thinking "what the heck...?" if you haven't read Devil's Kiss.
Consider yourself warned.
I love this series (so glad it's a series!) Chadda makes Joss Whedon look like he's telling campfire stories to ten year olds, if that makes sense. Don't get me wrong - I drink the Joss Whedon Kool-Aide and watch anything that bears his name. But his darkest moments are nothing compared to what Sarwat Chadda throws at Billi.
To wit: Billi is the only female member of the (still active, if lacking in funds and numbers) Knights Templar. To add a twist that keeps things interesting - in Chadda's version, after the Pope turned his back on the Templars, they turned to fighting the beasts of hell: vampires, werewolves, ghosts, fallen angels, etc. Chadda's done his research - a tiny bit of googling adds credence to his plot lines and characters.
And then his methods of destruction are just this side of "never gonna happen" to keep me up at night.
So it's a great read for this time of year, but reading at Halloween might be a little cliche'd.
I fully recognize that this genre isn't for everything, but if it teenage girls fighting the supernatural is your cup of tea, you'd be remiss not to give these a shot. Trust me.
Book trailer for the first book: