Professor Monica Miller’s new book, “Slaves to Fashion: Black Dandyism and the Styling of Black Diasporic Identity,” features on its cover a color photograph of New York artist Iké Udé dressed in dark pinstripe trousers, soft gray side-buttoned shoes with matching gloves, and a long dark suit coat that just shows the cuffs of his checkered shirt, a yellow and red boutonniere pinned to his lapel. He is perched on the very edge of a low green-cushioned sedan, his side turned to the camera.