His was an unlikely stardom, arriving late as fashions and tastes in movie manhood changed to suit him.

“He wasn’t very tall,” Humphrey Bogart’s sometime co-star Mary Astor wrote. “Vocally, he had a range from A to B, his eyes were like coal nuggets pressed into his head and his smile was a mistake that he tried to keep from happening.”

Then there was the beauty queen turned model, half his age when they met, set off sparks onscreen and off. The newly-renamed Betty Joan Persky had an indifferent screen career, for the most part. It wasn’t until Lauren Bacall buried Bogie and became the permanent guardian of his legacy that she truly came into her own as an actress and regal presence, on stage and on the screen.

But her guardianship of that legend covered-up and otherwise misdirected the world into printing that legend, and not the truth about Bogart — the upper class drunk with self-esteem issues he took out on many a co-star, director or even close friend.

That’s the case William J. Mann makes in his crackling new bio, “Bogie & Bacall: The Surprising True Story of Hollywood’s Greatest Love Affair.”

If there’s a classic film buff on your holiday shopping list, this is the film book to buy this year. Digging into studio archives, letters and archival interviews of those who knew them, Mann tears apart every “sanctioned” and “Betty Bacall-approved” biography that preceded it to give us a clear picture of two screen icons and the romance that blossomed when “wife number four” showed up, and the history various film publicists and later she spent decades minimizing or simply erasing.

Mann tracks through the years of Broadway, touring show and summer stock struggles of Manhattan doctor’s son and prep school dropout Humphrey, the “dandies” and “cads” he played as a young stage actor, the myths invented about his military service, his torn upper lip and the like.

The earlier marriages are remembered and deconstructed. He and third wife Mayo Methot might have been caricatured in the Hollywood press as “The Battling Bogarts,” two hard-drinking, loudmouthed brawlers. But she was his champion to Warner Bros. and Hollywood at the key juncture in his career, as much responsible for Bogie achieving stardom at 40 as anybody.

Bogie’s widow had the biggest hand in rubbing her and two other earlier marriages — all were actresses — right out of the picture.

“Official” versions of how Leslie Howard insisted Bogart get the role of Duke Mantee in “Petrofied Forest” so that they’d reprise the roles they’d had in the Howard-produced Broadway blockbuster that became Bogie’s big break, are broken down with “facts.”

Movies and plays are sketched in, Bogart’s succession of career setbacks, and personal ones, are listed and laid bare.

And his character comes through, if not wholly unscarred, at least rendered in realistic strokes, foibles and all.

Bacall, on the other hand, finds her post mortem “version” of herself, her life and career and the ways she made herself famous wholly upended. The most eye-opening revelations of the book are about her pursuit of older, famous and powerful men in New York as a means of jump-starting her career. While we’re allowed to take the “bedroom eyes” beauty at her word about these influential “friends,” Mann allows us, even demands that we wonder about her single-minded pursuit of fame and the role of “the casting couch” in all of it.

Although the book is chronological, the structure — a couple of hundred pages of Bogie’s life and career struggles “pre-Betty” before we get into anything about that “love story” — and its thoroughness make it frontloaded and a bit out of balance.

But getting a handle on the noble, public image of Bogart that Bacall preserved and the drunk who, like cafe-owner Rick Blaine, had to be goaded into taking action against injustice, unfairness and fascism at home and abroad, takes time. And Mann manages this with barely a misstep.

The picture of Bacall that emerges jibes with the one chance I had to interview her, when “Pret-a-Porter/Ready to Wear” premiered. Flirtatious in that sexy voice that she cultivated thanks to Howard Hawks, an indolence that tempered into “haughty,” she was forced into her “keeper of the flame” role by disappointing men (Sinatra, etc.) and a film business that didn’t have enough use for her after Bogie’s death, she developed a friendly but regal air, adorable and fun, but someone you didn’t dare contradict.

As Mann hints, as with a fuller picture of Spencer Tracy, which only emerged after longtime companion Katherine Hepburn’s death, we were never going to see the “real” Bogie until Bacall passed from the scene.

And Mann dives into many of the scores of Hollywood autobiographies and biographies of people like Astor, their “Maltese Falcon” writer-director John Huston, and others, to flesh out and enliven a three dimension picture of legendary personalities who cultivated that legend, but who are at their most human in this myth-busting biography.

“Bogie & Bacall: The Surprising True Story of Hollywood’s Greatest Love Affair.” By William J. Mann. 633 pages, including index. Harper Books. $40.