The album has had "a slow progress to critical darlinghood"; for the most part, audiences have remained nonplussed. According to Simon Goddard, most critics regard it as "[Nico's] defining avant-garde masterpiece". "The Rolling Stone Album Guide" considers "The Marble Index" the point in Nico's discography where "the difficult listening starts", and the album is "pretty amazing for it". Anthony Carew of About.com called it "a suite of rootless songs written with little precedent" and "an astonishing haunting, the work of a woman who, even whilst alive, seemed a lot like a ghost". Anthony Thornton of "NME" called it an "artistic triumph": "Bleak but beautiful, this album remains the most fitting embodiment of her doomed glamour." According to "Spin", "Few records, before or since, have sounded lonelier, spookier, or more desolate". "Trouser Press" described it as "one of the scariest records ever made".