In J. Hoberman’s telling, there’s nothing easy about New York’s avant-garde. Much of the art described in Everything Is Now was difficult to be around, sometimes aggressively so. The Museum of Modern Art’s guards asked to wear sunglasses in the optically jarring 1965 exhibition “The Responsive Eye.” During a Village Vanguard performance that same year, LeRoi Jones and Archie Shepp told their “predominantly—predictably—white, liberal, middle-class” audience, according to Vivian Gornick’s write-up, that “the only thing you can do for me is die.” Openings involved midnight screenings, spectators vomiting, confusion. A flyer released by Yoko Ono and La Monte Young warned their audience to “come prepared to sit on the floor” of Ono’s unheated Chambers Street loft for a six-month series of concerts; it also emphasized in all caps that “THE PURPOSE OF THIS SERIES IS NOT ENTERTAINMENT.” The sheer number of works from the 1960s that were “brutal and exhausting,” in the words of one poet describing a competitive jam session, overwhelms. The filmmaker and musician Tony Conrad used strobes to expand on William Burroughs’s …