Trent Reznor of Nine Inch Nails has always drawn energy and inspiration from a single emotional vein. Call it impassioned despair. But on “With Teeth,” NIN’s fourth studio album, we encounter a happier, healthier Reznor.

The music is still dystopic, and many of the lyrics are delivered in a scream. But the man behind them appears to have a new outlook on life. He has been through rehab, and has moved out of his converted funeral home in New Orleans and back into the day-lit world. “Less concerned about fitting into the world / your world that is / because it doesn’t really matter / no it doesn’t really matter,” he sings almost jauntily on the new song “Only.” NIN fans are right to be nervous.

Throughout his career, now spanning 16 years, Reznor has shown a remarkable steadfastness in the raging, changing currents of pop. His musical innovation was to marry the bleak, industrial sounds of Skinny Puppy and Ministry with the new-wave pop of Depeche Mode and Adam Ant – and to do it at a time when guitar gods ruled the altrock landscape. (His first song, “Down in It,” was actually a minor dance hit.)

“Pretty Hate Machine,” released in 1989, was synthy yet brutal. It introduced the world to Reznor’s unique sound and his disturbing vision: a kind of cyberpunk, S&M, Southern Gothic. The songs were perverse and manic, full of nihilism and graphic sex references. But they also had a good beat and you could dance to them.

Subsequent albums have broadened Reznor’s musical range while reinforcing his basic themes. “Downward Spiral,” his long-delayed follow-up finally released in 1994, was bolder and brawnier. It opened with the sound of someone being flogged and ended with the woozy, whispered intensity of “Hurt.” Its most memorable moment, however, was the oft-bleeped refrain “I want to f– you like an animal” from the surprise MTV hit “Closer.”

After another five-year intermission came “The Fragile”: Reznor’s grand, atmospheric, quixotic double album that set delicate, plinking piano numbers against throbbing electronic screamers. But the release of “The Fragile” revealed a fragile personality – one on the verge of collapse.

Thought it debuted at no. 1 on the Billboard chart, the album produced no hit singles (owing more to a changed pop music environment than the quality of the songs), and quickly fell from view. Reznor found himself playing to half-full stadiums and retreated into heavy drug and alcohol abuse. “It led me down a very dark and terrible path,” he recently told Spin magazine. “At the end of it, which was close to four years ago, it was very clear to me I was trying to kill myself.”

He may have recovered his health, but Reznor is still smarting from the lackluster sales of “The Fragile.” In response, he spends the first half of “With Teeth” spitting out radio ready songs. The first single, “The Hand That Feeds,” has all the makings of a NIN masterpiece: the booming war drums, the pixilated keyboards, the dance-y bounce and throat-lacerating final chorus. But it lacks danger. Reznor can’t seem to tap the same animal rage, the same searing self-disgust, that animated his earlier work. Instead of biting the hand that feeds, he licks it in hopes of being scratched behind the ears.

It sounds like he’s playing it safe throughout – a curious move for an artist who has always found success in being shocking and confrontational. All of the themes and musical ideas on “With Teeth” – even all the samples – are drawn from NIN’s back catalogue. Rarely do they achieve their former effectiveness. “You Know What You Are?” alternates between racing-heartbeat drums and Reznor’s signature squall-of-sound cacophony. It’s the same fight-and-flight approach he used in songs like “Wish” and “March of the Pigs,” but it lacks the same gut-punch intensity and startling originality.

After the obsequiousness of the album’s first half, Reznor swings to the alternate extreme, forgoing song structure altogether. With its growling, sludgy, melody-less beat, “The Line Begins To Blur” is aptly named. The final two songs, “Beside You in Time” and “Right Where You Belong,” likewise toy with anti-dynamics. The music consists of a single pulse – emerging from background to foreground – and spare piano. The songs seem to be striving for the minimal, slow-burn grandeur of “Hurt” and “The Day the World Went Away,” but fall short.

The album’s failing might be summed up by another lyric (taken out of context): “I wish this could have been another way / I just don’t know what else I can do.” Reznor has suffered so long, and made such good use of suffering in his art, that he knows no other way to proceed. On “With Teeth,” he’s still gnawing halfheartedly at the same old wounds, but without the same taste for blood.

Nine Inch Nails will play the Hammerstein Ballroom May 15-17.