What's the Name of That Book??? discussion

I'm looking for a book I read a few months ago while browsing through Books-A-Million. I only remember two stories, one is about a family who moves into a new house with their two children, a boy and a girl. Soon they start seeing a little girl with blond hair who only plays with the daughter. Soon that father finds a playhouse on the edge of the property and the daughter plays there with the ghost until the whole playhouse is sucked underground.

The second is about a single father who lives alone with his daughter, I don't remember much but he starts thinking that his daughter is possessed or has been replaced. In the end of the story he falls ill and calls his brother, who comes over and finds the daughter holding a doll made of candy that looking like her father. The brother tries to take it away from her and she bites the head off and a scream is heard from upstairs.

I hope this isn't too confusing, I've been searching for the book for sometime, I also want to say that it has the word "nocturnal" in the title but I'm not certain.

WOW I can't wait to find out what this is!

I'm really hoping someone figures this one out soon!! It sounds really good!

Found it! It's "Nocturnes by John Connolly."