The very first novel I ever read as a kid! It's consistently one of my favorite books, and the story holds up from age 7 to age 30... so that gives this book tons of points. I read it every few years, and I still enjoy it greatly every time.
Cute and fun with adorable illustrations peppered throughout. One caveat - I haven't seen a recent edition (my copy is from 1950), but unless things have changed, the illustrations should be by "Davine."
One of my favorite books as a child -- one of my earliest too -- and to my surprise, when I read it as an adult, I still loved it. A delightful twist on the fairy/human changeling tale -- in this story, the exchange of infants is interrupted, and nobody is certain which child is which.