Lottie, Pog and the Runaway Ghost By Sally Rippin

Lottie Baker has her dad, Bill, and her dog, Pog. That's more than enough family for any ten-year-old girl, isn't it? Besides, their house is already way too crowded without trying to squeeze anyone else in.

But then Lottie meets a runaway ghost called Martha May Claringbold, who is not too young and not too old. Martha doesn't want to live in the graveyard anymore because it's dark and smelly, and terribly dull. She wants to live in Lottie's room because once upon a time Lottie's room was her room.

And Martha may be just the one to help Lottie's secret wish come true.