Nearly 40 years after its initial release, The Rocky Horror Picture Show remains amazingly popular. Still shown at midnight screenings around the world, it has the distinction of being the longest-running theatrical release in film history, having originally opened in 1975. Not bad for a bizarre, low-budget horror-comedy rock musical that introduced “sweet transvestite” Dr. Frank-N-Furter (Tim Curry, making an iconic movie debut) to the general public. Even younger audiences have become part of the phenomenon, with the hit TV series “Glee” paying tribute to Rocky Horror in director Adam Shankman’s (Rock of Ages, Hairspray) season 2 episode “The Rocky Horror Glee Show,” featuring cameo appearances by original cast members Barry Bostwick and Meat Loaf.

The history of this weirdly influential film is recounted in Dave Thompson’s The Rocky Horror Picture Show (Limelight Editions, 150 pages, $9.99), the latest entry in the Music on Film series (other installments include books on A Hard Day’s Night, Purple Rain and This is Spinal Tap). The book goes deep into the origins of the musical, which was written by actor-composer Richard O’Brien (who plays Riff Raff in the movie) and began life on the London stage in 1973. With its oddball mix of dark humor, cheesy horror and catchy glam rock (its classic songs include “Science Fiction/Double Feature” and “The Time Warp”), the musical remains unlike any other—which is perhaps why Rocky Horror has sustained itself for so long.

For all its goofy charm and bawdy sex humor (which was quite daring for its time), O’Brien, interestingly enough, sees the film as an archetypal fairy tale: “Brad [Bostwick] and Janet [Susan Sarandon] are basically Hansel and Gretel and Frank-N-Furter is the wicked witch. That’s its true longevity. It’s not just pantomime and nonsense; it has this unspoken depth which makes it so appealing.”

Though the film was barely promoted by its distributor, 20th Century Fox, it took on a life of its own when late-night screenings started popping up around the country. Word of mouth spread, and before long Rocky Horror had attracted a genuine cult following, one of the first of its kind. Says O’Brien, “Millions of people have seen Rocky Horror now, but it’s still a cult experience, that’s the paradox.” People come dressed as their favorite characters, talking back to the screen and enthusiastically singing along to the music. Audience participation proves a key component in the film’s enduring success. Thompson says the film “remains the world’s first and finest interactive media experience, a virtual world before virtual reality was dreamed of, lived out on a worldwide web that predated the Internet by almost two decades.”

Perhaps Jim Sharman, director of both the film and original stage production, sums up the appeal of Rocky Horror best when he says: “There’s something classic about The Rocky Horror Picture Show that…escapes easy categorization, the fans know it—and that’s why it’s alive today. I’ve often described it as a big home movie, and in that sense it captures a moment in time in a way that has proved curiously timeless. Technically, there’s plenty that could be better, but then it wouldn’t be what it is.”

Whether you’re a long-time Rocky Horror devotee or someone new to the cult sensation, this quick, entertaining read is sure to make you want to pop the movie into your DVD/Blu ray player with renewed appreciation and do the time warp all over again.