WHAT IT’S ABOUT: Harvard professor and PBS star Henry Louis Gates Jr. explores African-American life and history since the mid-1960s, with one goal, according to the program notes: to chart “the remarkable progress black people have made while raising hard questions about the obstacles that remain.” Gates is your tour guide, and he conducts many interviews, from the world of TV (Shonda Rhimes) to the world of politics (former Attorney General Eric Holder).

MY SAY: As worthy, intelligent, sweeping and absolutely necessary as this four-hour film is — and caveat emptor, I’ve only seen the first two — “Black America” still often feels like a survey. Even the best of surveys can’t avoid that one flaw: They’re ultimately superficial. “Eyes on the Prize,” TV’s greatest film on civil rights, got around this by sheer tonnage. Airing over 14 hours in the late ’80s and early ’90s, “Prize” was as much encyclopedia as film, but anyone who watched couldn’t say they didn’t understand — or even feel — the struggle.

“Prize” was immersive. Perhaps of necessity, “Black America” is not. Right up front, Gates hints at the challenge before him: “The story of race in the second half of the 20th century would turn out to be much more complicated than we thought.” Along with his many other gifts, Gates also appears to be master of the elegantly turned understatement.

“Black America” begins March 7, 1965, with the march on Selma, then races ahead — through Stokely Carmichael’s momentous voter registration drive in Lowndes County, the creation of the Black Power movement, the movement’s break with Martin Luther King Jr. and on to James Brown and “Say It Loud (I’m Black and I’m Proud),” the black arts movement, and the launch of “Soul Train.” Viewers will learn a lot but understand less. Where’s Eldridge Cleaver and “Soul on Ice”? No mention of Huey Newton either. Gates scarcely hints at the controversy surrounding the Black Panthers.

You may occasionally feel the impulse as I did to hit the pause button, in a reflexive action easily interpreted as: Tell me more. For example, there’s a fascinating overview in the second hour about the paradoxes of integration and “structural racism,” along with an interview of Harvard sociologist William Julius Wilson, who coined the phrase. But that’s over almost as soon as it starts. You can almost imagine Gates checking his watch. Gotta move along. Have to get through the Reagan era in the next 10 minutes.

As usual, Gates is at his best when he’s talking with average people, like the first family to integrate Laurelton, Queens, but less so when he’s talking with the boldface name. “I was rooting for ya, brother,” he says to Jesse Jackson of his 1988 run for president.

Oh, brother.

But — as usual — I’m rooting for Gates. Fans of his other major films on black life and history don’t arrive expecting a hard-edged interlocutor anyway, but a congenial guide to one of the most important and urgent issues of our time. They’ll get that guide here, along with the intelligent interview. They may wish at times that they’d get a lot more.

BOTTOM LINE: Perfect timing arriving a week after a controversial election in which race was a huge factor — but neither deep enough, nor detailed enough.