When President George W. Bush met with Chancellor Angela Merkel of Germany in the Oval Office this month, the talk turned to Merkel's childhood under Communism, then wandered into the subject of Bush's latest bedtime reading: "Mao: The Unknown Story," an 814-page biography that presents the Chinese dictator as another Hitler or Stalin. Participants in the meeting say that Bush spoke glowingly of the book, a 10-year project by Jung Chang, the author of the hugely successful memoir "Wild Swans," which has sold 10 million copies worldwide, and her husband, John Halliday, a British historian. "Mao" has been at the...