On Friday, the New York Times premiered a new trailer for 56 Up, the latest installment of the "Up Series," a set of British documentaries. It began in 1964 with 7 Up, for which Granada Television brought together 20 7-year-olds as a cross section of British society, inspired by the Jesuit motto "Give me a child until he is seven and I will give you the man." Though it was not part of the original plan, Michael Apted, a researcher on that film, has since interviewed 14 of those subjects for a new documentary every seven years.

A few have dropped out occasionally—there has never been a contract obliging the participants to appear, though Apted did start paying them for their part with 28 Up. All but one of those dropouts has subsequently returned, however. When 56 Up premiered in the U.K. back in May, the big surprise was that Peter Davies, a no-show since 28 Up, was back.

If you haven't seen any of the films before, it's hard to describe their enormous appeal—and I'm not sure this trailer really captures much of it. Roger Ebert has said that the "films penetrate to the central mystery of life," which sounds awfully grand, but seems right to me. In Slate five years ago, Ann Hulbert pondered the attraction of the movies, and decided it had something to do with seeing "how fleeting life is, how ineluctably yet unpredictably time changes us, how inevitably the limitless potential of childhood is eroded." There is something incredibly moving about following lives that aren't scripted, from childhood all the way through middle age.

That genuine unscripted-ness is part of what makes the series so different from reality television—which didn't exist, of course, when the first film aired, but which became "the big gorilla in the room between 42 Up and 49 Up," according to Apted. In the latter of those two movies, one of the participants, John, said he didn't see much difference between that lowly genre and what he and the others were committing to the screen. "It's actually real-life TV with the added bonus that you see people grow old, lose their hair, get fat. Fascinating, I'm sure, but does it have any value, that's a different question."

It is, and the answer is yes, though it's not easy to explain exactly why. If you haven't watched any of the movies, I highly recommend catching up with one or two—you needn't watch them all, or in order—before January, when the newest one has its American premiere.