The author of ten books featuring the character Mary Poppins, P. L. Travers still prefers to use initials instead of her chosen name of Pamela Lyndon. Born Helen Lyndon Goff, she adopted this nom de plume to bring herself as close as possible to her father. She is equally reserved about the details of her life. She has given few direct glimpses of her Australian childhood, her Irish father and Scots-Irish mother, or her early addiction to writing and acting. She described herself in a 1966 interview with Richard Lingeman as "a very private person" and "rather shy of publicity." Travers has been just as forthright yet inscrutable with other interviewers. For her interview of the same year with Joseph Roddy she held forth on one of her favorite topics: "I don't write for children at all. I turn my back on them." Her answer to repeated questions about...