Charlotte Mosley"s careful collection of Nancy Mitford"s and Evelyn Waugh"s delightfully careless letters immerses one in a lost whirl. The two writers met in London in the late 1920s, but their correspondence didn"t take off until mid-World War II, when it quickly became an exaggeration-fest. Mitford, for example, matches Waugh"s surreal reports from Europe with one about an M.P. swelling up before his fellow politicians" eyes: "Well, it took 2 ambulances to get him away & now he lies on 4 beds with his trunk hanging out the window. Let nobody say that war time London lacks fantasy." For the next 21 years, these gifted gossips would render the ridiculous sublime and vice versa, turning (and then only mildly) serious in discussions of reading and writing, preferring to glide over the problematic and emotional. Throughout, Mitford likes to play the euphoric, lazy pupil, Waugh the master grammarian, theologian, and meanie. The exchanges on their own works in progress--particularly on Brideshead Revisited and The Pursuit of Love--are an important addition to literary history, but the book"s true exhilaration lies in Mitford and Waugh"s knowing--and knowingly vile--comic timing. Irresistibly offensive.