“When Trumpets Call” (Simon & Schuster, 512 pages, $30) is a bully biography. Like her subject, Patricia O’Toole does not mince words. Her Teddy Roosevelt is a world-class egomaniac, a voracious big-game hunter, and a vociferous politician. Even his relinquishment of power, refusing to pursue a third presidential term, is a self-satisfied gesture that aligns him with the country’s founding father.

While this view of TR is a familiar one, it is graced with Ms. O’Toole’s gift for felicitous phrasing and her penchant for exploiting sources others have underutilized. A case in point is Captain Archie Butt’s correspondence, written during the period from 1908 to 1912, when he was assigned to William Howard Taft’s White House. Not only was Butt Taft’s constant companion, he had also been a confidant of TR and was uniquely placed to assess both men during the period when TR concluded that his protege had reneged on the progressive platform he had expected him to enact. Others have certainly made use of Butt’s published letters, but the resourceful Ms. O’Toole checked the microfilm copies and discovered that Butt’s editor had censored a good deal – especially those passages dealing with Taft’s health and Butt’s reflections on the tensions between TR and Taft.

Drawing not only on Butt and a multitude of other sources, Ms. O’Toole presents a riveting account of what went wrong between TR and Taft and of how TR decided to run for president under the banner of the Bull Moose party in 1912. Yes, there was a Superman comic book quality to TR, who convinced himself that only his progressive breakaway contingent of Republicans could restore truth, justice, and the American way.

The scholastic Wilson and the judicious Taft made wonderful foils for the rough riding Roosevelt. TR scoffed at Woodrow Wilson as a weakling. No one would believe that Wilson was having an affair, TR told a staff member who brought the scandalous rumor to him, because Wilson had the demeanor of an apothecary clerk. In TR’s view, Taft failed because he was not a proactive president. In a way, Ms. O’Toole plays TR’s game, for much of her narrative emphasizes Taft’s phlegmatic, timid nature, which was bolstered by an inherent conservatism.

To TR, Taft had slowed the momentum of change and kowtowed to Republican conservatives. To Taft, who revered the law, change had to come in good order, however slow. He was aghast at TR’s proposals for popular referenda that could overturn court decisions. Believing it his destiny to preside over the Supreme Court, Taft regarded the presidency as an interruption, which he endured largely because TR had helped usher him into the job and Taft’s wife coveted the role of first lady.

The very quality that led to TR’s rejection of Taft was, however, exactly why Taft had ended up succeeding him in the first place, as Ms. O’Toole shrewdly shows. Taft was such a good lieutenant, so cheerful about following President Roosevelt’s orders, and so flattered by Roosevelt’s bestowing of his mantle, that Taft became president to please his friend and spouse.

The biographer concludes, however, that the trouble was not so much a timid Taft as a bullying Roosevelt, who could not admit the “immensity of his need for power.” That need was expressed out of office through his adventurous, year-long safari in Africa and later a harrowing expedition to Brazil, during which TR came very close to losing his life. In both instances, he may have cloaked his exploits as scientific inquiry (he brought along anthropologists who collected specimens for museums), but he also was seeking renown and was quite willing to die with his boots on.

Ms. O’Toole is concerned most of all with telling a good story. She never misses an opportunity to heighten the conflict between an indolent president and his energetic predecessor. And while this story is true enough, she withholds a measured passage, which if placed earlier in the narrative, would have marred the melodrama:

Passive and naive, petulant, resentful of opposition, Taft had failed as a politician, but his presidency was hardly a calamity. For better and worse, Taft had enforced the antitrust law with considerably more vigor than the Trust Buster. He cut the government’s spending, turned a budget deficit into a surplus, and collaborated with Congress to secure a series of reforms worthy of the Square Dealer’s administration: safety regulations to protect miners and railroad workers, a new federal agency to see to the well-being of children, an eight-hour day for federal employees, and an act requiring employers to compensate workers injured on jobs done under government contract. He also braved the opprobrium of the reactionaries to support a constitutional amendment for an income tax on the rich. Posterity would ignore Theodore Roosevelt’s contempt for William Howard Taft and usher him to a middle rung on the ladder of presidential greatness.

I can forgive Ms. O’Toole’s sleight-of-hand – let’s call it the sport of biographers – because she is a charming and playful writer. Describing one of TR’s journeys that includes another of his escapes from death when a train crashes into a boulder, she adds: “Apart from the cowcatcher, nothing was spoiled but the pleasure a biographer might have taken in devising a subtler portent.”

This is high-gloss biography, well researched and witty.