Calvert stated that Nirvana's "Smells Like Teen Spirit" has an "iconic place in history" as it had "generation-defining resonance" for young people from its era"; he states that "no other band ... made the urge to self-destruct ... as listenable", with "authentic" pain and "disaffection. Calvert also calls the record "chart history's most ferocious, dark and intense" music since early punk rock, and he says it was "heavy when heavy was needed" by young people of that era, "jarr young America awake" and giving them something to "cling to" in difficult times. A 2017 book stated that grunge "..forever changed the identity of rock music in a way analogous to punk"; moreover, grunge added "introspective" lyrics about "existential authenticity" and "what it means to be true to oneself". Grunge's Kurt Cobain has been called the "voice of Generation X", playing the same role for this demographic as Bob Dylan played for 1960s youth and that John Lennon played for the 1970s generation. Bob Batchelor states that Nirvana was "as important as Elvis or the Beatles."