This book is NOT the original Interior Castle of St. Teresa of Avila. It is a modern translation written to remove all "religious dogma". Much of it is not even translation, it is re-writing. It is a new-age, feel-good attempt to have one's cake and eat it, too. The arrogance is astounding.
If you are a Catholic or other person looking to read the actual writing of St. Teresa of Avila, avoid this (translation by Mirabai Starr) like the plague.