As Halloween approaches, and with it frightening opportunities for video on demand, it bears repeating that few American movies of any genre have possessed the ferocious energy and sociocultural stamina of 1968's "Night of the Living Dead."

Unleashed on a public rattled by real-world violence, the sort whose coverage on the nightly news made even one's living room feel scary, George A. Romero's bare-bones, black-and-white, blood-and-guts-strewn vision of zombie apocalypse provided nothing remotely akin to comfort.

What it delivered instead was the gnawing sense that karma was becoming downright ravenous; that one's survival of chaos was more likely contingent on brute force than on brainpower, and that our recent dead weren't about to take their condition lying down.

In '68, one influential trade publication deemed Romero's audacious intro to flesh-eaters an "unrelieved orgy of sadism." But strong-stomached drive-in and grindhouse audiences made it a cult film (and a proto-indie box-office sensation), while the Museum of Modern Art's early '70s purchase of a print for its permanent collection made the picture a certified classic.

Over the decades, attempts to reanimate "Living Dead" have naturally run amok. There has been an unruly mob of big-screen homages, parodies, remakes and ripoffs; Romero's own slew of sequels (five at last check); the "Left 4 Dead" video-game series; "The Walking Dead" on TV, and the viral zombie pub-crawl phenom, stumbling to a watering hole near you.

Meanwhile, the original movie, owing in part to its up-for-grabs status in the public domain, has been not only colorized, but voraciously re-edited, as well as rescored — most recently at the Trylon microcinema in south Minneapolis, where local multi-instrumentalist band the Poor Nobodys has been providing its own live soundtrack to the film. (The group's final pair of "Living Dead" shows takes place Sunday at 5 and 7 p.m.)

As regards VOD, not all "Living Dead" streams are created equal, resolution-wise, so beware; even the best of the film's many YouTube versions (free with ads) appears milky and scratchy. But the HuluPlus edition (available with subscription) is relatively clean, and the SnagFilms stream (with ads) looks even clearer, if a touch soft around the edges.

The Amazon Instant Video rental costs a few bucks, but, even in standard definition, this version's viscera verily glisten. Although the zombies have caused plenty of folks to buy the farm, we among the living still get what we pay for.

Also notable on VOD

Amazon also has "Birth of the Living Dead," a new documentary about how the young Romero, a college dropout from the Bronx, changed the course of American cinema and spawned a "billion-dollar zombie industry," in no particular order.

Like its subject, "Birth" is low-budget, but it's less than ingenious or even scrappy, relying for much of its worth on a single Romero quote — to the effect that the director's intent with "Night of the Living Dead" was not to restore the appearance of order, as in horror films past, but to upset it.

Among Romero's variably brilliant sequels, "Dawn of the Dead" (1978) and "Survival of the Dead" (2009) are available for rent on Vudu, "Day of the Dead" (1985) on Amazon and the underrated "Land of the Dead" (2005) on Vudu, Netflix and Xfinity Streampix. Alas, on VOD, Romero's "Diary of the Dead" (2007) remains lifeless.

Rob Nelson is a National Society of Film Critics member whose reviews appear regularly in the trade magazine Variety.