The Stones of Green Knowe, by L.M. Boston (1976), is the last of a series of six books written about an old house and the children who have inhabited it over the years. The spirits of these children travel through time--the first of the series, for instance, describes how Tolly, a 20th century boy, meets three children from the time of Charles II.
In this book, the central character is Roger d'Aulneaux, son of the Norman lord who first built the stone manor house that would become Green Knowe. Young Roger thrills to the sight of the stone walls going up--with windows! a chimney! a second story!--all very different from the cramped and smoky wooden hall they family had lived in before. That same summer, he finds up on a hill beyond the manor two ancient stones, shaped into rough seats. He discovers that the power of the stones can send him through time, and he travels to the future, where he meets the other children and is reassured that the house he loves still stands hundreds of years from his own time.
This is a descriptive book, rather than an action packed adventure. There are no dramatic happenings. The magic is fascinating--not only are the stones magic, but there is a smith, descended from the Vikings, who works his own ancient magic with metal--but the magic is not dangerous, or fraught in Exciting Ways. The time travel here is essentially sight seeing. So the pace is somewhat slow, especially the beginning.
But for those who love books with an incredibly strong sense of place, and who love their own special places, will feel a kinship with Roger as he sees the changes that take place at Green Knowe over the centuries. And it is the best description I have ever read of how to build a Norman manor!
It's not necessary to have read the earlier five books--the characters from those books reappear, and so it's nice to see them again if you know them already, but it won't be confusing. On the other hand, there's no reason to read this one first, and I think it will pack a greater punch if left to the end, as a coda to the series as a whole.
Note: I find it really annoying that Jacob, the West Indian boy from the Regency Period (I'm pretty sure he was a slave back there, but can't remember) is forced to talk as follows: "Me knows Feste [a horse]," said the black boy. "Jacob understands animals very well." Utter yuck. I've never re-read the book in which he is a central character, The Chimneys of Green Knowe.
But someday I really want to go visit Lucy Boston's home, which inspired the series!