What is the theme in The Missionary Position: Mother Teresa in Theory and Practice by Christopher Hitchens?

At least as far back as Shakespeare, disguise and deception have been prominent among literary themes. When a character pretends to be someone or something other than who that person really is, disguise and deception work on both literal and symbolic levels. Agnes Bojaxhiu dons a nun's habit and becomes Mother Teresa, saintly provider for the poor of the world, which prompts Christopher Hitchens to ask if she really is who she appears to be.