Books like The Diamond in the Window

A very unusual house...Eddy and Eleanor Hall have always known that their family was a bit out of the ordinary. After all, they live in one of the most remarkable houses in all of Concord. But they never guessed just how extraordinary their house really is, or what tremendous secrets about their family's past it holds. That is, until they discover the magical attic room with its beautiful stained-glass window, abandoned toys, and two perfectly made-up, empty beds that seem to be waiting, perhaps for two children just like themselves....