It’s a curse on gifted artists — listeners can tell when they’re marking time. Van Etten’s third full-length more than holds its own, but coasts on occasion. After a modestly roughened midtempo opener comes “Give Out” (a clear-eyed ballad of personal surrender) and “Serpents” (where she stands up against guitar-and-drum growls). Sequenced back-to-back, these show off the singer-songwriter’s dazzling expressive range so completely as to set a high bar. Van Etten positions herself as a strong and direct medium for exposing the depth, breadth and obscure corners of a woman’s personal confusion. So it’s a shame when “Kevin’s” comes on, with a strum-and-coo ambience that hauls everything over to the Mazzy Star recycling center. Two tracks later, there’s another stretch of dreary atmospherics, but the arrangement eventually heads into fresher territory. And so the pattern is set: Whatever Van Etten places into her own track as a challenge — whether it’s odd harmonies or subtly chugging rhythm shifts — she’s up for it. Her best comes forth when she’s challenged.