What exactly is Fantastic Beasts about? Three films in, J.K. Rowling's sumptuous, inscrutable series remains a mystery, a lacquered box of whimsy that lives just adjacent to Harry Potter and somehow much further from a sensical plot. Though that's hardly for lack of investment: Like the first two installments in the franchise, the latest (in theaters April 15) comes overstuffed with movie stars — can anything be wholly bad when Mads Mikkelsen is there to curl his lip? — opulent CG set pieces, and stray bits of flair, mostly in the form of its slithering, glimmering creatures.