I finished reading Charlotte Sometimes (the 1969 edition) while on a short little overnight camping trip a couple of weeks ago.
I found out about this book on the PUBYAC listserv. It was actually a Stumper, the librarian who asked the question giving details about a later edition of the book and not recognizing it as the classic 1969 version.
The story is about a girl, Charlotte, who lives in a boarding school. One night she changes places with another girl, Claire, who lives in the very same boarding school but forty years earlier. Apparently this changing-of-places has to do with the bed that they both sleep in. And they change places for only a few days at a time, at first. In the original version the two girls communicate with each other via a diary that Claire writes in during Charlotte’s time. The plot thickens when Charlotte (during Claire’s time) is moved to a different place to live, thus, removing the means to get back to her own time period. She is afraid that she will be stuck in the past so the rest of the story is spent trying to find ways back to the boarding school and the “magic bed.”
According to the listserv, the later edition has some details in it that are different. I am planning on reading tht one, too.
I really enjoyed this story. It’s too bad that it is out of print. Our library doesn’t even own it anymore. I have a feeling, though, that the publisher will release it again. It really is a classic.