New York ? It took 35 years, but historian Edmund Morris has finally been won over by Theodore Roosevelt.

“It’s impossible not to like Theodore Roosevelt,” the Manhattan author said last week following publication of “Colonel Roosevelt,” the third and final volume of his biography of the 26th president. Morris, whose initial 1980 installment, “The Rise of Theodore Roosevelt,” earned him a Pulitzer Prize, came to view TR as an “enormously positive and unusually important American figure who represented the best of his times.”

The new 766-page tome follows Roosevelt from when he left the White House in 1909 until his death in 1919 at age 60. As with the rest of TR’s life, that final decade was packed with memorable episodes.

“All writers like to write about action,” Morris said. “There are several intensely dramatic episodes” in Roosevelt’s final act.

The book begins with TR’s famous African safari collecting specimens for the Smithsonian. It was a photograph of that trip that first inspired Morris’ interest in TR as a 10-year-old growing up in Kenya.

He continues with Roosevelt’s nearly successful Progressive Party campaign to regain the White House in 1912. While on the stump, he was shot in the chest by a would-be assassin but insisted on finishing his speech before going to the hospital.

And there’s an account of his near-fatal exploratory trip in 1913-1914 down an Amazon River tributary now named for him, and the heartbreak after his youngest son Quentin was killed in World War I.

Midway through the first multivolume biography of TR ever written, Morris took a 15-year break to write 1999’s “Dutch: A Memoir of Ronald Reagan.” At the time the author said he liked President Reagan but doubted he would have liked Roosevelt “because he’s actually the opposite of everything I am — the outdoorsman, frenetically active.”

After finishing Volume 2, “Theodore Rex,” the story of the White House years, in 2001, and now the third book, Morris’ view has shifted. “I like him. I’ve just written a book about an enormously positive and unusually important American figure who represented the best of his times. It’s hard not to like a man of that quality,” he said.

Morris still sees faults, “particularly the bloodthirstiness of the hunting.” He also regards TR as preachy and self-righteous.

Morris said his research, which began in 1975, relied heavily on TR’s own writings. “He produced an enormous number of essays and articles after he left the presidency that had really not been looked at, including some remarkably scholarly essays on subjects like the conflict between evolutionary biology and religion” — an argument that endures today.

Recent surveys of historians have ranked TR as the fourth-greatest president after Lincoln, Washington and Franklin Roosevelt.

“He deserves his current ranking,” Morris said. “His overriding greatness as a president was his conservation philosophy, which was radical for its time and which a hundred years later is generally agreed to be his greatest legacy.” In addition, “he stood for the decency and dignity of the United States, because he was profoundly democratic and believed that government should be the greatest power in the land restraining the great corporations and making sure that democratic standards prevailed.”

Morris said TR’s story carries a lesson for the current occupant of the White House.

“Exactly 100 years ago in the midterm elections of 1910, TR, even though he (had turned the presidency over to William Howard Taft and) wasn’t running for office himself, was utterly humiliated” because Democrats were resurgent “after many, many years out of power.”

But Morris won’t be writing about politics anytime soon. His next project, he said, will be short, rather like 2005’s “Beethoven: The Universal Composer” and it “will probably be a figure in the arts. Not politics.”