Adam Sisman is the author of “Boswell’s Presumptuous Task,” a study of Boswell’s “Life of Johnson.” Novelist Beryl Bainbridge has written “According to Queeney” about Dr. Johnson’s relationship with his friend, Mrs. Thrale. Both writers talk with Steve Paulson about Boswell and Johnson and Boswell’s immortal biography of the brilliant 18th century man of letters.