Last week, Sterling‘s Union Square Press imprint celebrated its one-year anniversary with a reception at the Rizzoli bookstore on 57th St. Editorial director Philip Turner (front and center) was flanked by authors Marc Gerstein and Alan Weisman, with Greg Mitchell, Shane O’Sullivan, Sidney Blumenthal, and Kerwin Swint lining up behind them. And that’s just one-fourth of the 24-book roster that USP has put out in its first twelve months…