When Mark Levin was a teenager, he loved coming into Philadelphia from Elkins Park and visiting Independence Hall. In the room where the Declaration of Independence and Constitution were debated, he would imagine the founding fathers designing a nation.

"My parents always taught me to be thankful that I lived in this country and to appreciate the people who created such a marvelous society," Levin recalls.

Even at a young age, Levin (pronounced luh-VIN) realized that the cardinal aim of the men who composed our nation's sacred documents was to preserve liberty and repel tyranny.

Liberty and tyranny - Levin vowed that someday he'd write a book with that title.

Now a nationally syndicated radio talk-show host, lawyer, and president of the Landmark Legal Foundation, Levin, 51, kept that promise. His book, Liberty and Tyranny: A Conservative Manifesto, is No. 2 on the New York Times best-seller list after three months in the top spot, with about 800,000 sold.

Levin is also popular on the air. His show has attracted seven million listeners and is carried by stations in 47 of the nation's top 50 radio markets (weekdays, 6 to 9 p.m., on WNTP-AM [990] in Philadelphia), he says.

Liberty and Tyranny has received scant notice from the mainstream media ("Absolutely amazing," fumes Brent Bozell, president of the Media Research Center. "It underscores everything we've ever said about the incredible bias.") It has been hailed by conservatives.

"The book is phenomenal," says Sean Hannity, the political commentator and radio and TV host. "It defines, in a brilliant, thoughtful way, the meaning of conservatism."

"It's a magnificently written statement of conservative principles," says Morton Blackwell, president of the Leadership Institute, which teaches promising conservatives how to succeed in politics and government. "I predict it will become a classic."

Not everyone is smitten. In the Pittsburgh Post-Gazette, the rare metropolitan newspaper to publish a review, book editor Bob Hoover dismissed Liberty and Tyranny as "a slight effort" and "a best-seller largely on sales to conservative book clubs."

"The contrast between the work of serious historians and the reworked scripts of a talk show is impossible to miss," Hoover writes. "His book is . . . nothing more than an echo of other right-wing radio DJs who threaten to drown him out."

Few professors of politics, especially those of a liberal bent, have put the book atop their summer reading list, it appears. Several figures in publishing and academia who were contacted for comment said they had not read it, nor were they familiar with Levin.

"Never heard of him," said Ross Baker, a professor of political science at Rutgers University. "I don't listen to a lot of radio ranting."

The book is not a breezy beach read. Levin's radio listeners, accustomed to his snarling put-downs, might be disappointed. For Liberty and Tyranny is exactly as advertised - a conservative manifesto, a collection of serious, scholarly essays that seek to define the essence of conservatism.

Levin argues that conservatism has a distinguished pedigree. Its principles were embraced by the founding fathers and embodied in the Declaration of Independence and Constitution. Those documents provided the framework for a civil society that is based on moral order, that recognizes man's God-given natural rights, and that exalts individual freedom and private property.

Levin writes scornfully of liberals, whom he calls "statists" because they believe in the righteous omnipotence of the state. Statists view the Constitution as a malleable "living, breathing document" that can be tweaked and twisted to fit the temper of the times and to pursue utopian ends, he says. Today, the federal government has become "a massive, unaccountable conglomerate," Levin contends, that is regulating the lives and limiting the liberty of the citizenry through "soft tyranny."

Citing a recent Gallup poll showing that 40 percent of Americans identify themselves as conservatives, compared with 21 percent who view themselves as liberals, Rush Limbaugh says Levin's book "quenches a thirst."

"Too many on our side are defensive about our principles," Limbaugh says. "Mark is not. Mark is always on offense."

Levin was recruited to write the book by Mary Matalin, editor-in-chief of Threshold Editions, the conservative imprint of Simon & Schuster Inc.

The author of two other best-sellers - Men in Black, about the U.S. Supreme Court, and Rescuing Sprite, about a beloved mutt whose death devastated him - Levin has been surprised by the book's success.

"People are picking up the book because they want to know what conservatism is and why people would lean right, especially after a big election loss," says Kathryn Jean Lopez, editor of the National Review Online. "They want to know that they're not alone in the age of Obama."

The second of three boys, Levin grew up in Erdenheim and Elkins Park. He skipped his senior year at Cheltenham High School and began college at Temple University's Ambler campus. He took additional courses during summer, graduated at age 19, and enrolled in Temple's law school. That same year, determined to reduce property taxes, he won a seat on the Cheltenham school board.

After law school, Levin worked briefly for Texas Instruments, then joined the Reagan administration. After serving in a variety of posts, he became chief of staff to Attorney General Ed Meese at age 30.

"I've always been 'going on 50,' " Levin quips of his fast-paced career. "I was 2 going on 50, 12 going on 50, 35 going on 50. Now, I'm 51 going on 70."

Levin's day job is as president of the Landmark Legal Foundation, a conservative public-interest law firm. Headquartered in Leesburg, Va., it has a staff of six, including four lawyers. "We're a lean, mean, conservative machine," says Levin, who is paid $254,000. The foundation's 2008 budget was $1.6 million.

Over the years, the foundation has gone to court to uphold the constitutionality of school vouchers and pursued the Environmental Protection Agency for improper record-keeping, teachers' unions for using tax-exempt dues for political purposes, and former President Bill Clinton for lying under oath in the Paula Jones case.

Levin spends the rest of his waking hours preparing and broadcasting his radio show.

He grew up listening to WWDB-AM and WCAU-AM, and Dominic Quinn, Bernie Herman, Joel A. Spivak, Bob Grant, and Jean Shepherd. He calls himself "a professional talk-show listener."

"I know quality when I hear it and dreck when I hear it, and that makes me tougher on myself," Levin says.

The discourse can sometimes be less lofty than the Federalist Papers, Levin admits.

"We do rock and roll from time to time," he says. "I like the whole spectrum of intellectual engagement, whether it's confrontational or more cerebral."

Levin lives in Loudoun County, Va. He is the father of a college-age daughter and son, and his wife, Kendall, volunteers at a humane society and a homeless shelter. He shares his home with two dogs.

"I'm a dog lover first and foremost," Levin says.

Bob Beckel read Levin's book about Sprite at about the same time he lost his dog. He found it "very touching." A Fox News political analyst, Beckel was manager of Walter F. Mondale's 1984 presidential campaign and describes himself as "one of the rare liberals who is an admirer of Mark's work."

"I enjoy listening to his bluster," Beckel says. "His politics are off the wall, but his writing is very good. A lot of people on my side think he's a mean, evil guy, but a mean ideologue couldn't have written a book like the one he wrote about Sprite.

"He's also one of the smartest guys I've run across. I wish that mind were on our side. What a terrible thing to waste! We'd love to have him."