When we’re first introduced to emaciated, bug-eyed, trembling Bobby Liebling, the 50-ish frontman of the frequently dormant cult metal band Pentagram and the subject of this small-scale but weirdly engrossing documentary, he’s showing off his past stage outfits: perfectly preserved hip-huggers purchased in 1967, “paisley shit,” chiffon scarves. “I was saving them for when I got big. And that never happened, so I saved them forever,” the crack, heroin, and meth addict says in the sub-basement of his parents’ Germantown, Maryland, home, where he has resided for decades. In the kitchen, Liebling’s chain-smoking mother seems inured to the fact that her son will become a rock-and-roll suicide. But he promises his chroniclers, Don Argott and Demian Fenton, that he will not die: “If you guys want me around, I’ll stick around.” That, astonishingly, he does, even managing to get his career back on track, provides the arc of Last Days Here, an affectionate look at a self-destructing maniac and his supporters which bluntly reveals Liebling’s total abjection without mocking him. Like Argott’s The Art of the Steal (2009), a lively doc on the Barnes Foundation, which was also facing a highly contested, uncertain future at the time, Last Days Here is invested in a subject often one pipe hit away from extinction. Argott and Fenton track Liebling for three years and briskly braid every hopeful moment with its concomitant setback, never resorting to the bottom-feeding rubbernecking that thrives on cable.