The crowd at Barnes & Noble on Friday night is excited but disciplined. Oh, they know all about discipline. . . . These are the feverish fans of E L James’s “Fifty Shades of Grey,” the erotic novel that brought S&M out of the closet and into the suburbs. Spawned last year in the dark waters of online fan fiction, “Grey” has grown into a mega-selling trilogy, topping e-book and paperback charts.