Few Americans have spent more time near the center of power than Donald Rumsfeld, whose widely commented-on memoir offers many previously undisclosed details about his service with four U.S. presidents. We follow his rise from a middle-class childhood to the Navy to a seat in the U.S. Congress at age thirty, and his experiences there during the Vietnam War and the Civil Rights era. We also get his unique perspective as a cabinet-level member of the Nixon and Ford administrations, as CEO of two Fortune 500 companies, and as a special envoy to the Middle East for President Reagan.   Rumsfeld also addresses the challenges and controversies of his time as Secretary of Defense during the 9/11 attacks by al-Qaida and the wars in Afghanistan and Iraq. He includes candid observations on the differences of views within the Pentagon and with other members of President George W. Bush’s National Security Council.   In a famous press briefing, Rumsfeld once said that “There are also unknown unknowns . . . things we do not know we don’t know.” His book makes us realize just how much we didn’t know.