What is the theme in Under My Skin by Doris Lessing?

Another theme is truth. The author addresses this subject in the beginning pages of the book, and promises to tell the truth as far as she can without hurting anyone. What emerges is a story told chronologically, true to the facts, but revealing little about Doris Lessing's emotions and passions.

Lessing's version of the truth appears to be defined as telling the events of her life, providing snippets of personal experiences through memories, and downplaying some of the major events by just listing them and not exploring them in more detail.