The author mentions that she kept a diary and that she has always had an extraordinary memory (obvious with all the dialogue she had to memorize as a very young actress). Add in her access to letters belonging to her mother, and the result is an autobiography with amazing memory details going back to toddlerhood.
Shirley's book is an interesting glimpse not only into her life but also into the movie industry under the contract system. Many actors and actresses and studio heads are discussed as seen through the eyes of a little girl and later as a teenager and adult. Shirley Temple fans should find her autobiography pretty entertaining.