Take a photo of a barcode or cover
I discovered this novel in the Power Middle School library in 6th grade and must have checked it out and read it at least five times. I remember the cover of the hardcover book vividly. I've thought about it over the years and finally looked it up and ordered it. I have to say it didn't hold up as well as I was hoping. But it's still a good story and has made me feel a bit nostalgic.
From Kymm's and my discussion of William Sleator. She? or someone? said it was like Run, but just a few pages in, it's more like Poor Tom's Ghost with a soupçon of Wolves of Willoughby Chase. And huh, unexpectedly my new favorite. It's not going to displace House of Stairs or Into the Dream, but a book set in an old, maybe haunted, house in England, with a dollop of actual history, is likely to, and does, trump a book set anywhere else. (I overlooked the ample supply coal in the cellar of a house so inaccessible it doesn't have running water or electricity in a contemporary (early 1970s) first-world country.) It's unlike his later books, which all have a speculative element (e.g., a house of stairs, telekinesis, extraterrestrial life).