Food writer and cookbook author Michael Ruhlman joins us to discuss his book Grocery: The Buying and Selling of Food in America. Ruhlman combines his personal experiences with reporting to explore the origins of grocery stores, how they're designed and where our food comes from. He also looks at the current trends surrounding how and what Americans eat.  Michael Ruhlman will appear with Ruth Reichl and Dan Barber at the 92nd St. Y (1395 Lexington Ave., between 91st and 92nd St.) for an event titled "Farm to Market to Table: Where Our Food Comes from and Where it's Headed" on May 24 at 8 p.m. It will feature a book signing and talk. The event is sold out, but there is a waiting list.