ROGER AILES: Off Camera. By Zev Chafets. 258 pages. Sentinel. $26.95.

He’s been called “one of the few visionaries in the television business” and the “most successful executive” in TV; a Republican kingmaker who would become “the sharpest thorn in the side of Barack Obama” and a pit bull political strategist with only “two speeds: attack and destroy.”

Many of the clues to how Roger Ailes helped Richard M. Nixon, Ronald Reagan and George H.W. Bush capture the White House, and how he would make Fox News into the planet’s most popular cable news network, can be found not in Zev Chafets’ slapdash new portrait of him, but in Ailes’ own book from the late 1980s, “You Are the Message,” a book in which he frankly and presciently talked about the efficacy of appealing to an audience’s emotions, staying on offense and embracing television’s love of brevity, speed and colorful language. “Whether we think it’s a good thing or not,” he wrote, we live in a “headline society now,” and “you have to be punchy and graphic in your conversation” to hold people’s interest.

Ailes used his populism, showbiz savvy and political strategist’s canny understanding of creating narratives to build Fox News (started in 1996) into a huge profit machine for Rupert Murdoch’s News Corp. while helping to steer the country’s conversation to the right.

In doing so, Ailes has become one of the most powerful and debated figures in media and politics: an evil genius in the eyes of the many liberals who regard Fox News as a megaphone for Republican propaganda, and a prophetic hero to the many conservatives who applaud him for providing balance to what they see as the liberal mainstream news media. Like his channel, with its aggressive, in-your-face commentary, Ailes pulls few punches. He is famous for his combative swagger and tough-guy talk.

Chafets was given considerable access to Ailes and Fox News (which, he observes, “is usually about as reporter-friendly” as Tehran). And his book is regarded by some media watchers as an effort by Ailes to get out in front of another book about Fox by Gabriel Sherman of New York magazine (tentatively titled “The Loudest Voice in the Room: Fox News and the Making of America”), due out in late May.

When Ailes is center stage in this volume, he certainly commands the reader’s attention, whether he’s discussing political strategy and the show-business lessons he learned from his early days working for talk-show host Mike Douglas or dispensing acid apercus about today’s political landscape.

The overall book, however, reads like a long, soft-focus, poorly edited magazine article. For the most part, Chafets serves as little more than a plastic funnel for Ailes’ observations. Although Chafets supplies a bit of context here and there, he doesn’t ask his subject many tough questions.

Much of the later part of this book devolves into an oddly defensive attempt to rebut charges that have been levied against Fox News by critics on the left. There is little cogent analysis in these pages about how Fox News frames its reports from a conservative point of view, or the effect that this has had on the national conversation.

Reviewer Michiko Kakutani is a writer for The New York Times.