The reviews are coming in for Joanna Smith Rakoff's new novel, "A Fortunate Age," which is not named 'Brooklyn': The novel ably captures the zeitgeist, with venture capitalists financing magazines headed by M.I.T. prodigies and young people worrying about the gentrification of their Brooklyn neighborhoods. But where [Mary] McCarthy's histrionic rich girls enabled her to skewer contemporary mores, Smith Rakoff's are almost indistinguishable in their blandness.