Every fashionista worth her Louboutins cares as much about a book’s outfit as she does about its content. This purse-sized encyclopedia dons a cloth cover stamped with shimmering silver foil and a satin-ribbon page marker. Alongside vibrant illustrations, a team of fashion forecasters defines more than 285 terms from acid wash to zebra (“fatigues are really just exhausted clothes”) and answers sartorial quandaries (“What do I do when I’ve bought a genuine ‘Channel’ handbag in Hong Kong?”)....