Reiki: Hawayo Takata's Story is one of my three favorite Reiki books, one of the ones I read over and over again, give as gifts, and recommend to students whenever I teach Reiki.
Helen Haberly studied Reiki with Takata and promised Takata she would publish Takata's story. She talks about Takata's working methods as a healer and includes Takata's own teaching stories as well as the stories of Usui (who re-discovered Reiki, the ancient spiritual healing method) and Hayashi (who organized and ran an important Reiki center in Kyoto and eventually taught Takata).
Takata brought Reiki to the United States. Haberly clearly explains Takata's thoughts about how spiritual healing works and gives examples any Reiki practitioner could use.