The latest Eminem? Check. MJ bag? Yup. Brazilian bikini wax? Uh, hold up. Now that kids are demanding all the trappings of adulthood by the ripe old age of, oh, six, maybe they deserve something that’ll let them be kids. Minus all that god-awful Barney crap. Behold, the vintage children’s books collection at Brattle Book Shop, where the shelves are a veritable time machine, set for the years when kids’ stories were actually clever and characters were original enough to genuinely deserve the cults that would one day follow them — Eloise, Babar, and Amelia Bedelia. There are plenty of nineteenth century editions of classic Grimm and Andersen fairy tales and Aesop’s fables, plus newer classics like The Polar Express and The Velveteen Rabbit. All of it cool in a way that Tickle-Me-Elmo will just never be. And, for so-called grown-ups, flipping through them spells an equally charming — and a deliciously nostalgic — read. Yet more proof that behaving like an adult before you’re ready is just plain childish. The Brattle Book Shop, 9 West Street, between Washington and Tremont Streets, Downtown Crossing (617-542-0210 or brattlebookshop.com).