It is a book about Twitter and Instagram, and about having a good cry with the professional basketball player Tyson Chandler. There is advice about relationships and parenting, and a lesson about not being ostentatious told through understated drug dealers. There is a chapter that explores how white people, like the author, should be able to say "black lives matter."

But the character who pops up the most in this book is God.

"Own the Moment" is a book by Carl Lentz, the lead pastor at the New York City branch of Hillsong, an international megachurch that began nearly 35 years ago in Australia. With an engaging, casual voice and an easy humor, Mr. Lentz sidles up to the idea of a self-help book rooted in Christianity, and then aims for something different. The approach is not unlike the way his church has taken its place in American evangelicalism, with a decidedly unusual flavor that might even appeal to those who recoil from a typical Sunday service.

"I have a real palpable disdain for religious jargon. I grew up in church. I ran from church. I know a real Christian from a churchgoing nominal Christian better than most," Mr. Lentz writes. And on the day he found God, he adds, "I was riddled with fear. Things like 'What if this isn't real?' 'What if this means I have to give up everything that I love?' 'What if this means that for the rest of my life I have to listen to terrible Christian music and wear pleated khaki pants and get a haircut that looks like literally every single Alabama football fan?'"

Mr. Lentz, 38, is slender, 6-foot-2, with nearly a dozen tattoos and a preference for painted on skinny jeans. So far, no pleated khakis in sight.

Hillsong NYC holds most of its services at the Manhattan Center's Hammerstein Ballroom, a 2,200-seat music venue in Midtown, where it packs people in to four services every Sunday. Even at the 10 a.m. service, which has rows of stroller parking at the back, the room is dim, the smoke machines are going and music from the large house band swells like Coldplay with a heavy dose of resurrection.

On a recent Sunday, nearly a dozen people stood on a stage bathed in purple light, clutching microphones or guitars, pounding keyboards or drums, with another dozen forming a chorus behind them — Hillsong Church has a powerful recording label that is a dominant force in Christian contemporary music, and music is elemental to its services. A giant screen above the stage displayed close-ups of the singers with song lyrics stamped across the bottom of the screen so congregants could sing along. And sing along they did, flooding the concert hall with thousands of voices, outstretched arms and an enveloping emotional charge.

In the middle of a song about reverence, belted out from every corner of the concert hall, Mr. Lentz appeared onstage wearing hipster aviator glasses, tight black pants and a black blazer draped open over a low-cut black T-shirt. When the song ended, he delivered a fiery, and at times funny, sermon about being a Christian every day, as a man played the keyboard behind him. The sermon crescendoed near the end as he screamed into the microphone, neck veins popping, that sometimes we need to say to the "devil, temptation, shame, all that stuff: 'Your mama!' " As music surged back into the concert hall, Mr. Lentz walked off the stage peeling away his sweaty blazer.

"The way I try to preach is the way I tried to write this book," Mr. Lentz said, his words dancing with a hint of the South, carried through from Virginia Beach where he was raised. "I'm going to preach straight, and hopefully open a wide enough door that even if you don't believe what I believe, you can glean something from it."

"Own the Moment" is essentially written like a collection of sermons; Mr. Lentz said he constructed it so that each chapter is a stand-alone, the better to reach people who are not inclined to read a 300-page book. It is chatty rather than polished and occasionally hokey, populated by entertaining allegories and regular flashes of humor. There is a sprinkling of Scripture, but the text is not openly paved with it, and it is possible to forget at times that the book is written by a preacher. Until he reminds you that he believes that premarital sex is "not remotely optional, regardless of how many people try to say otherwise."

Mr. Lentz said that his previous writing experience came in the form of sermons and really long Instacaptions. He has more than half a million followers on Instagram, who are treated to pictures of his wife, Laura, who is also a lead pastor at Hillsong NYC, and their three children, along with the occasional shot with Oprah Winfrey or Justin Bieber.

The book also contains a small clutch of big names. Mr. Lentz tells a story about baptizing Mr. Bieber in a custom bathtub belonging to Mr. Chandler, who is 7-foot-1. Mr. Lentz also includes that he baptized Kevin Durant in a swimming pool.

Richard Flory, the senior director of research at the University of Southern California's Center for Religion and Civic Culture, said that evangelicals have a long history of hitching their Christianity to famous people as a way of drawing in congregants and making believers feel validated. Billy Graham had ties to Ronald Reagan, while the athlete Tim Tebow, the former action movie star Chuck Norris and the actor Kirk Cameron, have all been visible about their faith.

"That kind of celebrity culture weaves through evangelicalism really from the early 20th century," Mr. Flory said. "'Here's this enormously successful person, and they believe like I do.'"

But some have criticized Hillsong as too enamored of celebrity, a complaint Mr. Lentz appears eager to pre-empt in the "Disclaimers" section at the beginning of the book, where he says he hopes to harness the star power for "something redemptive and meaningful." Indeed, Hillsong has plenty of critics on either side of the aisle. There are those on the left who regard it as insufficiently open-minded on social issues, and those on the right who describe the church's theology as "thin" and say it strays too far from Christian orthodoxy.

"There isn't a great deal of historical Christianity or explicit theological content in their worship," said R. Albert Mohler Jr., the president of the Southern Baptist Theological Seminary. "I think there is a determined effort on the part of these churches," he continued, referring to Hillsong and others, "to avoid dealing with hard theological questions that might offend people."

Critics notwithstanding, the church has been growing fast. Mr. Lentz said it has 9,000 or 10,000 congregants in its 7-year-old New York City congregation and about 100,000 worldwide. It also draws a lot of young people and a fair amount of racial diversity, which many American churches struggle to do.

Observers say that Hillsong has stayed largely on the periphery of charged social battles, walking a delicate line as evangelicals running churches in liberal American cities like Los Angeles and San Francisco. Church leaders appear to have tried to create a welcoming environment for gay people, for example, without actually coming out in support of gay marriage. But Mr. Lentz has spoken out on issues of race in the past, and he devotes a chapter to it in his book called "If You're Racist and You Know It, Clap Your Hands." Mr. Lentz said that Opal Tometi, one of the founders of the Black Lives Matter movement, was a part of his church for several years.

"Racially speaking, are things better?" he writes. "Yes. But that statement is like saying, 'If you have been shot 10 times before and recently have only been stabbed five times, are you in better shape?' The issue is constant attack, not different types of pain."

Sitting backstage at the Hammerstein Ballroom preparing to give his sermon, Mr. Lentz said that while he long planned to write a book, and hopes that this is the first of many, this felt like an important moment to join the public conversation.

"There's some stuff that's really basic to me that I feel is in jeopardy right now, like decency, awareness, humanity. Stuff that shouldn't be complicated is complicated," he said. "I feel like the national climate has made it more urgent."

A few minutes later, he covered his tattoos and the frayed sleeves of his T-shirt with a blazer, walked out onstage into a flood of music and preached.