PRESENT SHOCK: When Everything Happens Now. By Douglas Rushkoff. Current. 296 pages. $26.95.

“Present Shock” is one of those invaluable books that makes sense of what we already half-know.

Playing on the title of Alvin Toffler’s influential 1970 “Future Shock,” which sounded an alarm about what Toffler called “a personal perception of too much change in too short a period of time,” Douglas Rushkoff analyzes a different phenomenon. The future arrived a little while ago, he posits: maybe with Y2K, maybe with Sept. 11. Now it’s here. And we are stuck with “a diminishment of everything that isn’t happening right now — and the onslaught of everything that supposedly is.”

Toffler warned that we wouldn’t be ready for this onslaught. Rushkoff is more analytical than alarmist. He divides his thoughts into five sections addressing five kinds of change, and his biggest illustration of present shock has to do with the book itself.

Because the present is more full of interruptions than the past was, it took him extra time to write. Because its ideas aren’t glib, he says, “Here I am writing opera when the people are listening to singles.”

“Present Shock” begins by simply describing how we have lost our capacity to absorb traditional narrative. It goes on to explain what we have used to replace it.

There was a time, Rushkoff says, when everything had narrative structure, even TV ads. Captive audiences sat through commercials that introduced a protagonist, presented a problem, then pitched a product to solve it. The little story ended well, at least from the advertiser’s point of view. But now viewers may be more angry than bored at such intrusions. They know that “someone you don’t trust is attempting to make you anxious,” so they ditch the ad before it’s over.

The ancient Greeks learned about the hero’s journey from Homer’s narratives. We’ve gotten decades of Homer Simpson, who “remains in a suspended, infinite present,” while his audience moves from one satirical pop-culture reference to the next.

Citing “Forrest Gump” as a film that failed to combat late-20th-century feelings of discontinuity and “Pulp Fiction” as one wild enough to usher in a new era, Rushkoff moves on to what came next: the video game open-ended structure that keeps TV drama in the eternal present.

Changes to news presentation are even more dramatic. This book describes the shock of politicians who, thanks to the 24/7 coverage ushered in by “the CNN effect” that began in the 1980s, “cannot get on top of issues, much less get ahead of them.”

Among the intuitive ideas turned tangible by “Present Shock” is “filter failure,” writer and teacher Clay Shirky’s term for what used to be called “information overload.”

Rushkoff’s translation: “Whatever is vibrating on the iPhone just isn’t as valuable as the eye contact you are making right now.” Your new boss isn’t the person in the corner office; it’s the PDA in your pocket.

In the end, only some of the ills in “Present Shock” can be chalked up to dehumanizing technological advances. “I am much less concerned with whatever it is technology may be doing to people than what people are choosing to do to one another through technology,” Rushkoff writes.

“Facebook’s reduction of people to predictively modeled profiles and investment banking’s convolution of the marketplace into an algorithmic battleground were not the choices of machines.”

They were made by human intelligence, because present shock’s ways of targeting, pinpointing and manipulating aren’t just shocking. They’re very lucrative, too.

Reviewer Janet Maslin is a New York Times staff writer.