Avid film fans are in technoheaven these days. Once you had to haunt art-house theaters or film festivals or cinema societies that screened out-of-circulation reels. Now at your fingertips are thousands of movies of all genres on DVD or Blue-ray discs and Internet streaming services that let you watch on command at your television or computer screen. And if your entertainment budget is limited, you can boot your computer and search YouTube or DailyMotion, where some kindly pirate is likely to have recorded a DVD or a broadcast on Turner Classic Movies and impermissibly uploaded it to the Net for anyone’s viewing pleasure. And should you have qualms about intellectual-property theft, you can watch your tax dollars at work in the DVD section of your local library by checking out a favorite or yet unseen flick for a few days or a week, at no cost (except for the overdue fine, which will probably be far less than the cost of a ticket at a first-run theater).

With seemingly unlimited numbers of films now inexpensively available — from high-art classics to the lowest-of-the-low drive-in “necking” movies — it may come as a surprise to bleary-eyed binge watchers that there equally exist (or once existed) thousands, of other films that no one is likely ever to see because they are what is now known as “lost.”

Phil Hall, a film journalist, critic, publicist, distributor, festival programmer, and actor, provides an insightful, entertaining and wide-ranging introduction to the who, where, what, why, when, and how of vanishing cinema in In Search of Lost Films (Athens, Georgia: BearManor Media). It’s largely a tale of cupidity, neglect, hard luck and, sometimes, wild rumor.

Hall starts off by quoting a 2013 report issued by the Library of Congress which reported that “at least 75 percent of the feature films made in the United States during the silent era are considered to be lost.” And that’s just American films; the Library of Congress report, Hall notes,  “offers no consideration of films made in other countries that are believed gone forever.”

How does a film get “lost”? Hall explains that from its beginnings, and well into the early 1950s, before the advent of scholarly interest in movies as cultural artifacts, Hollywood looked upon its product as just that — product — and had little interest than in the profits and shareholder dividends their “product” produced. The stuff of cultural history was immaterial to the studios. Once a film had in the course of a few years played every possible theater two or three times, it was retired to the studio’s vault. That vault was usually little more than a warehouse, often without adequate precautions necessary to preserving nitrate film, an unstable, highly combustible and potentially explosive substance. Not infrequently a film warehouse went up in flames, and its contents were destroyed. Or, if a studio’s finances were pinched, a retired film might be salvaged for its light-sensitive silver-based emulsion, which was washed from the film. The recovered silver was sold for its value as a precious metal, and the film itself might be sold to be cut up for guitar picks. More often, though, films simply deteriorated in storage and turned into dust.

If you thought that only movies starring “B” actors in “C” scripts have suffered this fate, consider that MGM somehow managed to “lose” The Divine Woman, Greta Garbo’s  fifth American film, released in 1928. All that remains is a nine-minute fragment (approximately one reel) discovered in Moscow in 1933.  (You can judge for yourself what, with a bit more care, might have been saved, as the Moscow fragment is available as part of a TCM Archives DVD, The Garbo Silents Collection [2005].)

Other less well-known but culturally important works now seem gone for good. Hall is especially informative about the loss of films by African-American producer-directors Oscar Micheaux and Spencer Williams. Independently produced — since Hollywood studios were long indifferent (when not hostile) toward black artists — their films were exhibited almost exclusively in theaters catering to African-American audiences, and printed in small numbers due to the high cost of making copies for distribution, which significantly weighed against these films’ survival.

Hall notes that Micheaux’s seminal silent works, Within These Gates (1919) and The Symbol of the Unconquered (1920) “exist today only because prints were located in Spanish and Belgian archives, respectively.” But his final film, The Betrayal, shot with a soundtrack and released in 1949 at a Broadway theater, has disappeared and is yet to be recovered.

Spencer Williams’s apparent masterwork, Brother Martin: Servant of Jesus (1942), has suffered a similar fate. Hall recounts that Williams, known today (if at all) for his role as Andrew Brown in the embarrassingly racially stereotyped 1950s televised version of Amos ’n’ Andy, had Hollywood bona fides as a bit-player during the 1920s, and broke the color barrier for black writers by fashioning gags for Al Christie’s comedy studio. Later, during the 1940s, Williams directed nine feature films for Dallas-based Sack Amusement Enterprises, which specialized in distributing motion pictures with all-black casts to segregated theaters around the country.

Brother Martin was a biopic about Martin de Porres, the illegitimate son, born in Peru in the late 16th century to a Spanish aristocrat and a freed African slave. De Porres became a lay brother in the Dominican monastic order of the Roman Catholic Church, and was beatified in 1837. (A century and a quarter later, he was raised to sainthood by Pope John XXIII.) Hall weighs the odds against Brother Martin at the box office: “The film . . . was certainly a gamble, as black Catholics represented a minority within a minority, while white audiences would not be reached by this all-black production.” We are unlikely ever to know whether Williams’s gamble might eventually have paid off. Except for a theatrical poster and two still photographs, no copy of the motion picture or screenplay has yet been found.

Lost films are not simply an American problem, and In Search of Lost Films treats the scope of the phenomenon. India, Japan, and Korea have theatrical film industries dating back to before the sound era. But in 2002 a devastating fire at India’s National Film Archive destroyed all but a dozen of 1,700 silent films housed there. Japan’s archives were devastated during World War II in the 1940s, and those of Korea suffered much the same fate during the Korean War of the 1950s.

The fact that more of cinema’s history and legacy has not disappeared is due overwhelmingly to a relatively small number of organizations dedicated to film preservation and restoration. Prominent among these in Europe and the United States are France’s Cinémathèque Française, the British Film Institute, the Nederlands Filmmuseum, and the Museum of Modern Art, in New York City. Hall also gives a special shout-out to Czechoslovakia’s Národni Filmovy Archiv, founded in 1943, during the Second World War. Hall explains that Czechoslovakia (now the Czech Republic and the independent nation of Slovakia) has been notable as a treasure trove of long-lost U.S. films because the country’s tiny film industry could not satisfy its domestic market during the 1920s.

After the war, when a Communist regime nationalized the film industry, all prints were gathered into a centrally controlled government archive. That act of ideological collectivism inadvertently saved, among other American films, Buster Keaton’s Three Ages (1920), and the only surviving nitrate print of Ramon Navarro and Francis X. Bushman racing their chariots around Hollywood’s idea of ancient Rome’s Coliseum in MGM’s 1925 production of Ben-Hur.

Then there are the unexpected epiphanies of film preservation, when lost works are resurrected in moments of sheer serendipity: A print of Carl-Theodor Dreyer’s director’s cut of The Passion of Joan of Arc (1928) was found in the closet of a Norwegian mental hospital in 1981, and the original version of John Cassavete’s Shadows (1959) “turned up in 2004 in the Lost and Found department of the New York City subway system.”

Finally, perhaps the most entertaining portions of In Search of Lost Films are Hall’s accounts of film enthusiasts’ quests for their own “Maltese falcons” — films that might (or might not) exist — such as Japan’s King Kong in Edo (1938); the early 1950s Space Jockey, which even director Phil Tucker unequivocally acknowledges to be “a real piece of shit,” and outtake footage of the custard-pie fight that almost concluded Stanley Kubrick’s 1964 Dr. Strangelove or: How I Learned to Stop Worrying and Love the Bomb.

You don’t know what you’re missing until someone tells you what’s missing, and cinephiles can thank Phil Hall for a highly enjoyable journey into cinema’s void.