The Art of Spiritual Healing
I'm a huge Joel Goldsmith fan. There are some differences, some more significant than others, between what he's saying and what Unity might say, but knowing your Goldsmith will absolutely make you a better Unity student. The distinctions throw our teachings into sharp relief, and the commonalities are powerful and supportive. You can't go wrong with any of Goldsmith's books, but this one, The Art of Spiritual Healing, is my favorite. If you want to learn how to pray, there are other places I'd recommend you start (more on that some other time), but if you want to learn how to pray with other people, which is J.G.'s bread and butter, it's hard to beat this book. If you're studying to be a practitioner, a chaplain, or any other position that involves prayer treatment, read this book. Then re-read it every couple of years. Trust me.