This is a graphic novel series aimed at about a 12-year-old's level. Courtney Crumrin is a fairly stock character: the rude, precociously misanthropic little girl who's brought to a new town by her callow, grasping, negligent parents, where they stay for free in a rich great-uncle's mansion while trying to climb the social ladder. Courtney has no friends and doesn't fit in, but soon discovers that her Uncle Aloysius has some interesting books and more interesting hobbies, and that all kinds of ghoulies and ghasts hang around the mansion, and the surrounding town.
Courtney has adventures with a goblin in the woods, meddles with magic to deal with bullies and her social isolation, and has to go rescue an infant she is babysitting from the Goblin Market. Finally, she is almost replaced by a doppleganger.
It's cute in places and Courtney has attitude. But not terribly original, and there seems to be no major metaplot; not surprising, given the target audience. Also, I was not a fan of the artwork, particularly Courtney and her fish-eyed, noseless face that makes her look like an alien Bratz doll.
It was okay, and I might read other books in the series if I see them at the library, but it's certainly not something I'd go out of my way to finish. I think children will find it far more resonant and creepy; I saw it as a Middle-Grade version of Tales from the Crypt