TV PREVIEW

“The Tonight Show Starring Jimmy Fallon”

11:35 p.m. Feb. 17 on NBC

Three years ago, veteran New York Times media reporter Bill Carter wrote a book about the first time Jay Leno left the “Tonight Show” in 2009 and Conan O’Brien took over for a brief period. I don’t know if Carter plans a sequel to “The War for Late Night,” but if he does write about Leno’s second departure from the show, it would have to be a smaller book.

That’s not just because the transition from Leno’s second regency to the arrival of the Jimmy Fallon era is going more smoothly , but also because who sits behind the desk on a broadcast network’s late-night talk show just isn’t as important as it was only a few years ago.

Jay Leno brought his second shift to a close on Thursday night after 22 years. “The Tonight Show Starring Jimmy Fallon,” or “TTSSJF” in TV shorthand, kicks off on Feb. 17 with U2 and Will Smith as the first guests.

Fallon’s show will return to New York from Los Angeles where Leno hosted, and it will be produced by Lorne Michaels, the “SNL” mastermind who also produced “Late Night With Jimmy Fallon” and, before that, “Late Night With Conan O’Brien.” Leno is older, of course, and more of a joke-machine than Fallon, who is at his best in sketch comedy.

That said, NBC has made a smart decision in tapping “SNL” veteran Fallon for the job previously held by Steve Allen, Jack Paar, Johnny Carson, Leno, and, for seven months, O’Brien. Fallon is young but not so much of an iconoclast that he’s going to alienate older viewers. In other words, he’s not Conan. He’s not as clever or as intellectually nimble as Conan, but he may not need to be. Having an “every-viewer” appeal is more of an asset now than it was during the tumultuous 2009-10 interregnum when Conan hosted “Tonight.” Back then, broadcast networks still had an occasional pipe dream of capturing younger viewers.

Fallon is the perfect choice for an audience that will only grow older in the coming years, because younger potential viewers have other things to do and other shows to time-shift view.

What is Leno’s legacy? No one can argue with his ability to write and tell a great joke. He is a master of standup, and in that regard, he stands apart from every other “Tonight Show” host. The first host, Steve Allen, was a good comic but he played best with others, with routines such as his “man on the street” interviews.

Jack Paar was mercurial, dry, intellectual—the Letterman of his day.

Carson, of course, was king. No one has come close to his genius on any late-night show and probably never will. He was a brilliant comic, having fine-tuned his timing by studying idols such as Jack Benny and Bob Hope. But unlike Leno, he was a great interviewer as well as a great monologist. He asked celebrities questions we would ask, then reacted as only a comic genius could. His deadpan takes were crazy great, perhaps even greater (forgive me) than Benny’s.

O’Brien wasn’t given enough time or network support to show us what he might have done with the “Tonight Show” over the long haul, but we have a good idea from his tenure hosting “Late Night” and, since 2010, with his TNT show. He has learned to be more at ease performing and interviewing his guests.

When O’Brien bridled against NBC’s decision to push the “Tonight Show” back a half hour to enable Leno’s return to late-night, after Leno’s prime-time experiment went bust, O’Brien’s younger fan base was outraged and made their displeasure known on “I’m With Team Coco” Facebook pages and elsewhere on the Internet.

Although NBC may have been in corporate denial, the angry reaction was the sound of a future kicking down the door of the present.

“Beneath his feet, Conan sensed the ground moving,” Carter writes in “Late Night Wars,” “shifting finally from a baby-boom-centric culture to one controlled by Gens X and Y.”

A few pages later, Carter describes a phone conversation between Leno and Lorne Michaels while the smoke was still clearing from the Conan debacle. The two men had little reason to chat much over time, Carter writes, but although Michaels saw Leno as “more of a Bob Hope-like figure — a safety valve for viewers…. Michaels realized that people in America tended to admire and accept a ‘well-made one-of-those, even if it isn’t a one-of-those they liked.’ ”

Now that Michaels is in charge of the “Tonight Show,” he’s anointed another “safety valve for viewers” in Fallon, who is, nonetheless, funny, likable and has Michaels in his corner. There’s nothing wrong with that — in fact, it’s exactly right, for some of the people, some of the time.

In other words, traditional broadcast TV viewers, in late-night hours.