YA Review. This is not an MG series. My son and daughter both recommend it for high school, due to some of the scary / frightening images and the amount of gore.
Thomas Ward was a Spook's apprentice in Chipenden, but his mentor is killed (before the book starts, in another series, so if you like this one, there's a whole other set of books to explore) and he's left to muddle on without him, learning as he goes.
But his mentor's books were destroyed in a fire, so when a creature begins attacking people from the village, he's not sure what it is or how to combat it. Compound that with a young girl, Jenny, who shows up asking to be his apprentice (not realizing he's barely able to cope as it is), and the fact that Thomas buried the Starblade, the only weapon effective against this creature, in his mentor's grave, and it's a recipe for disaster.
A witch named Grimalkin comes to help, or so Thomas and Jenny believe, but she's got an agenda of her own -- fighting the coming army of these creatures, called Kobalos, which want to wipe us out. Of course, her experiments might do the job for them, if Thomas and Jenny can't kill the creatures she sets loose.
I won't spoil the ending, just know it's gruesome in the middle and it doesn't end well for Thomas. There's not even a hint of romance between Thomas and Jenny. although both are full of angst, for their own (backstory) reasons.
SPOILER ALERT: If you haven't read the first book, this review starts with its ending.
Thomas Ward comes back from the dead, raised by an angel-creature related to his non-human mother after battling -- and winning -- the Kobalos champion sent to demoralize us all. We learn he's got amazing regenerative powers and as such, he's seized by a local prince and used to rally the troops for a preemptive invasion against the Kobalos.
But it's all been a big ruse and the Kobalos are waiting for Thomas and the prince's forces. Thomas rediscovers the girl who broke his heart, Alice, is a dark witch in on the plot and even Grimalkin doesn't see it coming.
This is where I exited the series. My two kiddos continued on to the third book and said it was good, if exceptionally bloody and gruesome. I have the third book, The Dark Assassin, on hold at the library.