"I love your style" is a phrase plenty of girls in this town hear once in a while. But the kind of gals who showed up at Diane von Furstenberg's studio last night—Anh Duong, Anne McNally, and Rachel Feinstein Currin—hear it a lot. And it's possible no one hears it more than Amanda Brooks, whose new book on the subject, I Love Your Style, was what everyone had gathered to celebrate.

The picture-heavy tome divides the way women dress into ten easy categories, explaining the ins and outs of styles ranging from Bohemian to Cheap Chic. Cecilia Dean was eager to take the test: The Visionaire editor thought she'd be a Classic ("I'm in head-to-toe Yves Saint Laurent right now," she reasoned). I thought she would be a High Fashion poster girl. Turns out we were both surprised: Brooks put her in the Minimal section. "You know what, she's probably right," Dean said.

Toward the back of the store, the first-time author was signing book after book, looking for a few surprises of her own. "No one has asked for a naughty introduction," she smiled. "But maybe I'll spice them up as the party goes on." Overseeing the proceedings was von Furstenberg herself. "I knew from a very young age the kind of woman I wanted to grow up to be," she said. "And I think Amanda is the same way. She is style."

— Derek Blasberg