Is there anyone with even a modest acquaintance with the history of the abolition of slavery who does not know the name William Wilberforce? If so, then perhaps, just perhaps, this is the book for you. Eric Metaxas resorts to the third-rate biographer’s buildup, assuring the reader that Wilberforce is forgotten. He changed the world, yet he remains unacknowledged. But wait! There is more: “Taken all together, it’s difficult to escape the verdict that William Wilberforce was simply the greatest English reformer in the history of the world.”

Confronted with the armada of blurbs on the back cover of “Amazing Grace: William Wilberforce and the Heroic Campaign To End Slavery” (HarperCollins, 277 pages, $21.95) Rebecca West’s retort comes to mind: “Writers on the subject of August Strindberg have hitherto omitted to mention that he could not write.” Mr. Metaxas slathers his prose with clichés: In only one paragraph, he manages to fit in “truth be told,” “pulled some strings,” and “power play.” And poor Wilberforce is still in grammar school!

And that’s not all: “The fire he ignited in England would leap across the Atlantic and quickly sweep across America.” Without Wilberforce’s leaping and sweeping, the cause of reform itself would have hardly survived: The “America we know wouldn’t exist without Wilberforce,” Mr. Metaxas writes. This is biography as infomercial. Not even Thomas Carlyle rivals Mr. Metaxas as a shill for the Great Man theory of history.

That Wilberforce was a key figure in British history is, of course, undeniable. It took him and his allies nearly 20 years, but they abolished the British slave trade in 1807, and Wilberforce lived just long enough to learn of the abolition of slavery itself in 1833. But this much is in the history books. Turn to Mr. Metaxas’s biography and you will see: He thanks John Pollock for his “entirely fabulous” “Wilberforce: God’s Statesman” (1977), Garth Lean for his “most readable” “God’s Politician” (1980), Kevin Belmonte for his “excellent Hero for Humanity” (2002), as well as other biographers who were a “tremendous boon.” Indeed, Mr. Metaxas has no new information to add, as he cheerfully admits, and perhaps that is why he foregoes any sort of documentation for his narrative.

The unfortunate result of this biographer’s hyperbole is to reduce the complexity of his subject, depicting Wilberforce as a saintly evangelical whose faith triumphed over a world that fervently believed in the rightness of slavery. Wilberforce did have a sparkling, “childlike affability” and a “becoming gracefulness,” to quote the American abolitionist William Lloyd Garrison. But Wilberforce was also a canny and patient politician, a British Member of Parliament who knew how to work the system, seeking powerful allies in figures like William Pitt, for example.

Mr. Metaxas seems to understand the present no better than the past: “There’s hardly a soul alive today who isn’t horrified and offended by the very idea of slavery,” he observes at one point. And later, “Slavery still exists around the world today, in such measure as we can hardly fathom.” Mr. Metaxas seems oblivious to the contradictoriness of his bloated prose because he evidently has no sense of history to show him that the world is never one thing. If there had been no William Wilberforce, Thomas Jefferson would still have had misgivings about slavery, and George Washington would still have freed his slaves. Gouverneur Morris would still have stood up at the Constitutional Convention and denounced Southerners for their peculiar institution. And Benjamin Franklin, who once had owned a slave as a body servant, would still have joined an anti-slavery society shortly before he died.

In other words, it was not Wilberforce against the world. To be sure, without Wilberforce, slavery would have likely persisted beyond 1833. Biography does alter history. But Mr. Metaxas commits the cardinal sin of biography: elevating the subject to ahistorical heights.

William Wilberforce is a great historical figure not because he triumphed over the retrograde beliefs of his epoch, but because he capitalized on a minority but emerging conviction that slavery was wrong. Mr. Metaxas is an admirer of Wilberforce’s evangelical Christianity and uses his subject’s piety as a kind of subtheme to tout the positive role of faith in public life. It may be so, but God save biography from the likes of Mr. Metaxas.

crollyson@nysun.com