It began in the late 1960s, and would last for about a decade—a cosmic shift in the landscape of horror movies. The “Old Horror” movies, which had been around for more than 30 years, featured cobwebs and musty old crypts; the “New Horror” movies were considerably more realistic and graphic. The central threat in these films came not from a supernatural entity, but from something more human—the neighbors down the street or maybe even a person living inside the protagonist’s home. By placing the horror in everyday settings, these films became much more frightening to audiences, and still have the power to shock today.

Jason Zinoman’s new book, Shock Value: How a Few Eccentric Outsiders Gave Us Nightmares, Conquered Hollywood, and Invented Modern Horror ($25.95, 274 pages, The Penguin Press) discusses in expert detail this critical time in movie history. Zinoman focuses on several of the most pivotal, influential horror movies of the ’60s and ’70s—among them Roman Polanski’s Rosemary’s Baby, George A. Romero’s Night of the Living Dead, William Friedkin’s The Exorcist, Tobe Hooper’s The Texas Chainsaw Massacre and John Carpenter’s Halloween. While this eclectic group of moviemakers came from very different backgrounds and shared differing sensibilities, they all were outsiders who understood the deep, unknowable darkness at the root of the horror genre. Their movies, Zinoman writes, “share a sense that the most frightening thing in the world is the unknown, the inability to understand the monster right in front of your face.”

Unlike earlier horror films—with their fantastical, neatly defined monsters, far removed from reality—the “New Horror directors thought that ambiguity and confusion are not only scarier than certainty, but reflect the reality of a world where the Vietnam War and Watergate are in the headlines.”

The directors’ upbringings had a profound effect on their moviemaking careers as well. Wes Craven, for instance, was raised by a strict, fundamentalist mother, who only allowed him to watch Disney cartoons. It wasn’t until college that Craven saw his first R-rated movie. Craven, who would go on to create the controversial rape-revenge classic The Last House on The Left, says, “I had so much rage as a result of years of being made to be a good boy… It makes you crazy.”

One of the most fascinating figures in the book is the lesser-known writer-turned-director Dan O’Bannon. While a student at USC’s film school, O’Bannon became friends with classmate John Carpenter, with whom he collaborated on their first feature, Dark Star. After leaving him in the dust after making Dark Star, O’Bannon became resentful of Carpenter’s burgeoning moviemaking career. A huge admirer of influential horror writer H.P. Lovecraft, O’Bannon got his own shot at success with his script for the 1979 classic, Alien. The movie’s most memorable scene, in which a baby alien bursts out of John Hurt’s stomach, was also the most personal for O’Bannon. The inspiration came from O’Bannon’s own struggles with Crohn’s disease, a stomach disorder which ultimately killed the underappreciated moviemaker in 2009.

If Shock Value has one fault, it’s that its focus is a bit narrow. While Zinoman focuses much attention on nine or 10 of the most critical horror movies from this period, he also misses out on some great ones, only briefly mentioning other critical figures of the time like David Cronenberg and Dario Argento. Yet these are minor quibbles. Shock Value provides a ghoulishly fun, thought-provoking read—one that is ideal both for horror movie buffs, as well as film history fans.

Although the devices and themes utilized in the pioneering films discussed—startlingly fresh and innovative at the time—have been endlessly repeated and recycled in the years since, their power can still be felt today. Zinoman perhaps best sums up the legacy of this unparalleled time in horror movie history when he says: “The New Horror movies are often celebrated for their raw documentary feel, their relevance to the times, how they reflect the national insecurities, but by the end of the seventies, they had transcended such limited descriptions. They were well known even by people who had never seen them. They had become modern myths.”