Before "Fred and Ginger," there was "Fred and Adele," a show-business partnership and cultural sensation like no other. In our celebrity-saturated era, it's hard to comprehend what a genuine phenomenon these two siblings from Omaha were. At the height of their success in the mid-1920s, the Astaires seemed to define the Jazz Age. They were Gershwin's music in motion, a fascinating pair who wove spellbinding rhythms in song and dance. In this...