A Sound of Crying was a book a read a bunch of times when I was in elementary school. The main character moves into a house and when she sleeps she dreams of a different girl’s life.
Anya’s Ghost is a fabulous graphic novel about identity and a bit of a mystery about how this other girl actually died.
The Shadowy Horses has one ghost of a Roman soldier. This is more of a romance and a historical mystery about the site the archaeologists are excavating though. Only the little boy actually interacts with the ghost, calling him the Sentinel.