Paul McCartney performs at Save Mart Center in Fresno, California on April 13, 2016. (Steve Jennings/Getty Images)

As a four-brained collective, the Beatles possessed a staggering oneness. Remove any individual skill set from that collective, and they would have been something else — something less — entirely.

It’s possible to be a passionate fan of the band and own every bootleg recording along with every Beatles book and yet still have little interest in the solo careers of the four members. That poses a particular challenge for biographers who set their eyes on just one of them.

In 1981, Philip Norman wrote “Shout!,” one of the finest Beatles biographies. There is no better record of their early days in the flesh dens of Hamburg. Norman also revealed himself as a writer willing to advance theories where facts feared to tread. He’d tell you what he thought was going on, even if his opinions could be a bit splashy or polarizing.

Now he’s back with a massive biography that focuses just on Paul McCartney. It wraps up ­Beatles matters about halfway through and isn’t very polarizing, but then again, McCartney himself rarely has been. Norman is thorough, though, and his book gives us a fuller McCartney than you’ll find anywhere else, in part because of McCartney’s studious management of his brand over the years.

Norman is not shy about the group’s flaws. The Beatles, trotted out so often nowadays for their surplus of love and acceptance, were, in fact, deeply sexist. Read a biography like this, and you’ll find them shockingly so. Beatles management was regularly trying to keep up with women with paternity suits. At the band’s triumphant post-“Hard Day’s Night” return to their home town in 1964, leaflets were printed on behalf of a Liverpool woman “denouncing Paul as ‘a cad.’ ” How would that have played out on Twitter?

"Paul McCartney: The Life" by Philip Norman. (Little, Brown)

The band’s breakup in 1970 plunged McCartney into a depression, and that accounts for some of the most compelling new material in this biography. People forget how young the Beatles were when the group ended: late 20s, basically. Norman captures just how daunting the future was for someone like McCartney. Having achieved so much, with the bulk of his life still in front of him, he felt overwhelmed by expectations of reaching those previous peaks.

Linda McCartney, who emerges as the love of Paul’s life — if we’re not counting John Lennon — was downright heroic during a time in which McCartney himself could barely function. “I don’t know how anyone could have lived with me,” McCartney says. “I was on the scrap heap in my own eyes. . . . It was a barrelling, empty feeling that just rolled across my soul.”

The Wings years are seen as chaotic and exciting — like a lite version of the Beatles — but the specter of those past relationships with the old band members hovers at the edge of almost every page.

There are some poignant glimpses of what might have been, before Lennon’s assassination in 1980. At the end of the 1970s, McCartney, George Harrison and Ringo Starr clambered up on a stage at a party to bash out a jokey version of “Sgt. Pepper’s Lonely Hearts Club Band.” The past is something better revisited with a joke than with an attempt to measure up to earlier glories, even for a genius like McCartney.

Music has been a key component throughout his life, of course, but what the book makes plain is a far bigger component, one that continues to this day: McCartney’s desire to live well. We see a man who must have a woman in his life. Family is his focus now, along with talking about John and the days of yore, and being Sir Beatle, the ultimate surviving rock star.

You just want to shake the McCartney of the final third of this book and say, Boyo, don’t you want to be a great artist again? Write something awesome — or try, anyway. But that’s one of the take-away themes of Norman’s biography: the idea that most of day-to-day life is spent by adapting, by humming along, rather than by standing up and pulling at stars.

But how you wish this guy would have kept pulling nonetheless.

Colin Fleming is writing a book titled “Same Band You’ve Never Known: An Alternative Musical History of the Beatles.”

Paul McCartney
The Life

By Philip Norman

Little, Brown. 853 pp. $32