Middle-grade ghost story - found!

[soundofsunlight]

I never got to read the whole book, so I don't know how it ends. What I do know:

There's a boy staying at an old house, possibly visiting relatives. He learns about the history of the house, including that the family who used to live there had a son who had died of a fever. Later, something happens, and our protagonist somehow switches places with the boy in the past. He wants to get back to his own time and his own body, and he tries to tell the family, but they assume he's just delirious from the fever. I think the ghost of the other boy may have purposely caused the switch, to get a chance to live. In any case, he does his best to pass as the protagonist and avoid going back to his sick body. I don't know what happens after that.

Is this familiar to anyone?