Social media sites are often derided as vehicles for narcissism, allowing people to broadcast quotidian events as if they were big news. Lou Beach, an illustrator whose work has appeared in The New Yorker, wanted to use his Facebook status updates for something more. He transformed them into tiny stories, compact little worlds that his friends and followers could enjoy. The catch: Facebook limits posts to 420 characters, the title of Beach’s new collection of 169 very short stories.