This is one of my very favorite of montgomery's books. From the back:
"At twenty-nine, Valancy had never been in love, and it seemed romance had passed her by. Living with her overbearing mother and meddlesome aunt, she found her only consolation in the "forbidden" books of john Foster and her daydreams of the Blue Castle. Then a letter arrived from Dr. Trent - and Valancy decided to throw caution to the winds. For the first time in her life Valancy did and said exactly what she wanted. Soon she disovereda surprising new world, full of love and edventures far beyond her most secret dreams."
This blurb doesn't do justice to the story, which has a couple of cool twists and the perfect ending.