For more than four years, 'N Sync member Justin Timberlake has been king of bubble-gum pop and teen heartthrob extraordinaire.

His group's album in 2000 broke records by selling more than 2 million copies in just one week. He inspired gushy fan Web sites galore and mesmerized the MTV generation with slick music videos. His catchy songs, such as "Drive Myself Crazy," with their sappy, uncomplicated lyrics, seemed to speak directly to the hormonally driven adolescent soul:

Now I toss and turn, 'cause I'm without you

How I'm missing you so bad

Where was my head, where was my heart

Now I cry alone in the dark.

But after years of fueling the Billboard charts, the popularity of formulaic boy-pop has fizzled, and, after its demise, comes the inevitable reinvention of the pop idol -- a sort of necessary Second Coming of Justin.

The 21-year-old begins his campaign to reconquer the pop world with Tuesday's release of his first solo effort, Justified, an album that is a significant departure from the sounds of 'N Sync. It has soul, it has a grooving '70s feel, and, at times, it has Timberlake ostensibly channeling Donny Hathaway and Stevie Wonder with a touch of Michael Jackson. The release also may be one of the most scrutinized new albums in recent music history.

"Debut records are pretty paramount for any artist, but especially for one who is trying to subtly reinvent himself," says Craig Marks, editor of Blender magazine. "People are really watching this record -- along with the new Christina Aguilera record -- to see how these artists can reposition themselves after the trend that they're associated with has kind of died out."

A different sound

Timberlake isn't the only member of 'N Sync who's exploring new avenues. J.C. Chasez is supposedly considering a solo album, as well; Lance Bass has made headlines with his quest to go into space; Chris Kirkpatrick has been pushing his fashion line; and Joey Fatone currently stars in Rent on Broadway. And who knows? With Justified, Timberlake may surprise critics, even those who have enjoyed slamming 'N Sync's work for years.

"It's a collection of the sounds that I've grown up on and that I like," the singer said in a recent conference call from his native Memphis, Tenn.

"I think the bubble-gum sound that -- and it's the closest thing, the closest words I could use so that people would know what sound I was talking about -- I think that that has changed," he added. "I don't think people want to hear that so much any more. I know that I don't, and that's why I did this record."

Working with some of hip-hop and R&B;'s hottest producers, including Brian McKnight, Timbaland and the Neptunes -- who boast recent hits with Usher, Britney Spears and Jay-Z -- Timberlake spent six weeks earlier this year co-writing all 13 songs. The new collection ranges from the Stevie Wonder-esque "Senorita" to the pop-infused, Latin-tinged single "Like I Love You" to the slow, seductive "Take It From Here."

In several, Timberlake does a falsetto that already has led to comparisons to Michael Jackson. (Timberlake himself fueled the MJ association at his debut performance of his first single, "Like I Love You" at this year's MTV Video Music Awards, in which he displayed Jackson-inspired moves.)

"Obviously, he's influenced our whole generation," Timberlake said. "As a fan, my favorite Michael record is Off the Wall, and the reason that I like it so much is because you can hear the rawness in the sound and everything wasn't so rehearsed back then.

"We wanted to record this record like they used to record records back in the good old days," he added. "There's moments on the record where you'll hear somebody in the background just shout out something, and we just kept it on the record. We weren't trying to make everything so perfect. I think the proudest part about the whole thing is that it does sound organic."

Attention-getter

His efforts have begun to win praise. Entertainment Weekly called Justified "the ultramodern R&B-pop; hybrid [Michael Jackson's] Invincible failed to be." And a Billboard review of his first single, "Like I Love You," stated: "Timberlake darts from a guttural whisper into a surprisingly soulful falsetto with an ease that wasn't evident during his boy-band heyday."

"Most people are rooting for Justin," Blender's Marks says. "He can certainly sing, he can definitely dance and he's learning to write his own songs, so he's basically got two out of three. If he can learn to write, he's certainly got a long career ahead. There's lots of room in pop music now for a big male pop star."

No one, however, expects Justified to scale the heights of 'N Sync. In 2000, 'N Sync's No Strings Attached shattered pop records by selling 2.4 million in its first week. The following year, its third album, Celebrity, sold 1.9 million in the first seven days. According to Nielsen SoundScan, which tracks music sales, the group's three albums combined have sold almost 25 million.

Since its Oct. 22 release, Timberlake's first single has sold 4,200, Nielsen SoundScan reports. By contrast, American Idol winner Kelly Clarkson's single has sold 506,000 in six weeks, and Pearl Jam's latest has sold 17,000 in two weeks.

But the comparison that may draw the most attention is that between Justified and Now or Never, the debut album of Backstreet Boy Nick Carter, whom magazines recently have linked with Timberlake ex Britney Spears.

"I'm really indifferent about that whole situation," Timberlake said of the alleged love connection. "At this point in my life, there were things that I said probably two months ago that I probably don't even feel the same way about.

"As far as Nick goes, I wish him the best," he added. "As far as anybody comparing the two of us at this point, I personally think it's kind of lazy. If you listen to [Carter's] 'Help Me' and you listen to 'Like I Love You,' they're two totally different songs, and you can tell that we're two totally different artists. ... After the records are both out, anybody who does compare it, I would have to say, 'Go listen to it again.' "

Those who have closely followed the he-said-she-said on magazine covers this summer after Timberlake's breakup with Spears also may find themselves picking apart lyrics in Justified for references to the relationship. In "Never Again," for example, he croons "Girl, you lied straight to my face, Looking in my eyes / And I believed you 'cause I loved you more than life."

Timberlake, however, shrugged off all speculation.

"Half the album does come from personal experience, but the other half is completely fantasized, made up," he added. "Once everything was written, I just took on the part of whoever it was in those songs. At the end of the day, they're just songs, and, as far as where I'm at, I'm as cool as a cucumber."

Busy schedule

Timberlake won't say more about his personal life at the moment, especially the rumored romantic links with actress Alyssa Milano and 'N Sync dancer Jenna Dewan. And for now, he's focusing on the new album. On Nov. 9, MTV is scheduled to air artistLaunch, a one-hour show that documents the making of Justified and follows Timberlake in the weeks leading up to his album release. Later this month, his music video for "Cry Me a River" will debut on MTV, and there are plans underway for an international tour sometime next spring.

No matter how well his solo foray goes, however, Timberlake still plans to return to 'N Sync.

"The fact that the guys in the group are my friends, that's what's inspiring to make another record, because you know that there's no egos, that everybody's doing what they're doing because they love to do it," he says. "And that's reason enough for me to make a record, even if it is a flop. ... Those are my friends and they'll always be my friends and I would never turn my back on them."