Leave it to Oprah to start a revolutionary American trend: reading. Chicagoans are now reading en masse Harper Lee's To Kill a Mockingbird. And former librarian Laura Bush is using the clout of her new job to get a few notable authors to read out loud in Washington. As host of the first National Book Festival, this weekend, the First Lady will oversee an all-day affair on the Capitol lawn with readings, music, food and lessons on bookbinding. Whom has Bush picked as opening acts for this bookfest? John Adams biographer David McCullough, novelist Gail Godwin (Evensong), playwright Larry L. King (The Best Little Whorehouse in Texas), short-story writer J. California Cooper, historian John Hope Franklin and TV anchor Tom Brokaw (The Greatest Generation). Brokaw, for one, practices reading out loud.