I began with Path of the Kabbalah by David Sheinkin, M.D. and was led to this book through that text. I knew absolutely nothing about Judaisn and the Kaballah and Sheinkin's book was the first place to start. I immediately had to get my hands on the real books of mystical Kabbalah. Kaplan's writing is outstanding. The repetition of information while new pieces are layered, more repetition, more layers is very effective. Then move on to Meditations and the Bible and/or Meditations and the Kabbalah, and the Zohar. Sheinkin's book mentions key writers such as Kaplan and Scholem, though the later is very critical and academic rather than accessible and ready to put into practice.
There is a lot of garbage that is printed on the various aspects of and subjects pertaining to Kabalistic thought and creation, but this is NOT one of them. Rabbi Aryeh Kaplan was a truly phenomenal man, worthy of praise from mystics, rabbis, and the curious alike. It is truly a wonderful coincidence for those lucky enough to meet or sit in on lectures with Rabbi Kaplan that he lived in the last century. Rabbi Kaplan made Kabala accessible to those whose only language is English. While I would recommend other books by this great man, I would also recommend, more than words can express, this work in particular. If you SERIOUSLY want to learn about the Kabalistic paths, this book is one of the best in English to help you along your journey, safely, and honestly. Good Luck!