Relates what happens to three American children, unwillingly transplanted to Wales for one year, when one of them finds an ancient harp-tuning key that takes him back to the time of the great sixth-century bard Taliesin.
I read this book not long ago; I know it's a "children's/YA" book, but I really enjoyed it anyway. I think it's a nice mix of real-life family problems among siblings and a very magical world that one of the siblings enters. I read this right before going to Wales, where the book takes place, and it made my trip that much more "magical."