Never has a band been more mockable, never has a band been more successful.

I find Bono more compelling the further he stands from God—though He’s always within shouting distance. Since the first song on the first album (“I Will Follow”) made an unambiguous promise, the band has been adopted by Christians—U2-themed worship has been a stable of youth services for years—yet the songs themselves rarely fit comfortably into notions of devotion. Even the refrain of their celebrated gospel hymn, “I Still Haven’t Found What I’m Looking For,” admits to restlessness in the face of certainty.

Particularly in the Achtung Baby era, Bono is in constant combat with his faith—challenging, decrying, and equivocating. He assumes the eminently reasonable voice of Judas on “Until the End of the World,” genuflects before a lover in “Mysterious Ways,” and on “Acrobat” sings that he’d “break bread and wine … if there was a church I could receive in.” On the follow-up, Zooropa, an album intended as a quickie EP but that grew into something even more sneakily ambitious than its predecessor, Bono drifts further into doubt. He sings of rejecting God, and yet, somehow, admits, “For the first time, I feel love”; then on “The Wanderer,” the album’s closer, the authoritative voice of vocal guest Johnny Cash acts as a mask for Bono’s confessional lyrics: “I went out there in search of experience, to taste and to touch and to feel as much as a man can before he repents.”

"I think I'd like to give a message to the young people of America,” Bono said while accepting a Grammy for Zooropa. “We shall continue to abuse our position and fuck up the mainstream." For a few more years, they mainly did. Scattershot anthems for films such as Batman Forever and Goldeneye led to an Eno-presided concept album of songs scored to imaginary movies. Planned as an actual U2 record, Original Soundtracks 1 was eventually released under the no-frills band name of Passengers, ensuring that few would hear the record and marking the moment when U2 stepped back from a precipice of outré experimentation and exhilarating folly. After offering pop radio the unmelodic, Edge-sung drone “Numb” during the summer of ’93, they put Luciano Pavarotti where a guitar solo is supposed to be on “Miss Sarajevo,” the only single from the Passengers record. I can’t speak for the young people of America, but Radiohead was certainly paying attention: A left turn like Kid A doesn’t happen without Achtung Baby and Zooropa. The market had been trained to accept such weirdness. Thankfully Radiohead also learned from U2’s ensuing lack of nerve and has never turned back.

U2’s next official release, 1997’s Pop, was an awkward, insecure, jungle-jam compromise—part hard dance, part soft rock—that finally began to push the band backward. With the turn of the millennium, All That You Can’t Leave Behind slowed their tempo and recirculated old, aging-fan-placating sounds, while Bono peddled ESL-legible, Bobby McFerrin-worthy clichés (“It’s a beautiful day, don’t let it get away,” “Home, that's where the heart is.”). In stark contrast to his speech seven years earlier, Bono spoke at the 2001 Grammys of "reapplying for ... the best-band-in-the-world job." Like the Rolling Stones, the last band to claim that hubristic and empty title, U2 honed and leveraged their brand as the music itself became less relevant. All That You Can't Leave Behind and its follow-up, How To Dismantle an Atomic Bomb, are hook-heavy, arena-ready rock machines. They're all front, emotionally arresting but uncharacteristically depthless. The Edge steals freely from his bag of riffs ("Miracle Drug," "Crumbs From Your Table"), and the once-mighty rhythm section gets buried deeper and deeper behind Bono's go-for-broke singing and lyrics that seem eager to please, eager to be at peace with their God and the world. How could the same man who moaned "With or Without You" write a line like "What you don't have you don't need it now"?

Promisingly, No Line on the Horizon (2009) was a comparatively messier, more uncertain affair, suggesting that the band might be feeling restless and hungry again (which might be the only reason to forgive Bono and the Edge's queasily effective experiment in Broadway bombast, Spider-Man: Turn Off the Dark). The problem is how ultimately these records lack everything that makes rock roll, that makes pop crackle, that makes soul. It’s not about coolness—it’s about desire. I can’t get no, you can’t always get, I can’t quit you, I put a spell on you, I still haven’t found, please, please me, why don’t we do it, wouldn’t it be nice, I saw her standing, how could you just leave me standing, burning, desire.  At its best, U2 doesn’t merely satisfy our desires, but takes us somewhere, marching into the shadows, exploring spaces within and without, risking failure and greatness, and giving us something worth confessing in the end.

Also in Slate: See the author's complete ranking of U2's albums, best to worst.