One danger of artistic longevity is repetition. Then there’s the problem of self-parody. In the case of U2, a band with 13 documented and doted-upon studio albums across 34 years, how does an artist deliver surprise instead of lapsing into well-worn tropes, even if they’re expertly imagined and executed?

One effective way to shock in 2014 is by dropping anticipated new work with no advance notice, for free, while the world is tuned to an Apple product launch. That’s how U2 just did it, anyway.

The long-gestating new one from Bono, the Edge, Larry Mullen Jr. and Adam Clayton is called “Songs of Innocence,” and during last Tuesday’s iPhone and Apple Watch media event the band simultaneously acknowledged the new record’s existence and, with the click of a button somewhere in Cupertino, California, dropped it for free into 500 million iTunes accounts.

Like a magician lifting a kerchief to reveal a dove, all of a sudden there it was, amid our iTunes files: U2, “Songs of Innocence.” Named for the first of a two-volume William Blake poetry cycle, the record is focused on nostalgia while being produced by a consortium of contemporary hit-makers — including Paul Epworth, Flood and Ryan Tedder — and overseen by the producer Danger Mouse.

Though “Innocence” doesn’t cost anything and you already have it, should you exert the energy to move your finger to iTunes and poke a few virtual buttons?

Sure, but don’t expect a record as breathtaking as U2 at its best. Rather, this is average-grade stuff with a couple essential songs. It’s filled with your typical Bono buzzwords — some so overused, like “light,” “stars” and “dream” — that you start to think U2 is messing with us, or, more likely, need to expand their themes.

“Songs of Innocence” is an autobiographical record about music as a salve, as an engine, and the ways in which it ferried Bono and band on a fantastic journey to wealth, fame, influence … and California. It delivers noble snapshots on the power of the Ramones and the ways in which lead singer Joey Ramone nudged Bono to take the mike, and the way in which Joe Strummer’s politics informed his music. On “California (There Is No End to Love),” the band revisits its first arrival in Southern Calfornia — while giving a musical nod to “Barbara Ann” and the Beach Boys.

Sonically, though, “Songs of Innocence” is a reactionary album defined by the tones of today. Thankfully, there aren’t any dubstep bass-drops, but it shouldn’t come as a comfort to anyone that the first few seconds of the record sound like a Lumineers ooh-aay-ooh song. Or that a Florence and the Machine vibe, courtesy of producer Epworth, cloaks other tracks in overwrought Wagnerian drama. Or that musically it’s about as dangerous as a Coldplay record, albeit with grittier distortion pedals; or that most of Adam Clayton’s trademark bass lines sound like rote imitations of better lines elsewhere in the band’s repertoire.

The menace lies elsewhere, and the band is at its best when in expansion mode. “Raised by Wolves” recalls the 1970s trauma that overwhelmed U2’s homeland one Friday at dusk, when simultaneous IRA bombings in Dublin and Monaghan killed 33 people. The striking “Sleep Like a Baby” opens with a heavy analog synthesizer and finds Bono’s voice, still miraculously evocative, enveloped in echo and strings. Soon, though, the Edge disrupts with a riff that throws the whole thing wonderfully off-kilter.

“Volcano,” too, surprises with a dance-rock track that sounds inspired by LCD Soundsystem and the DFA posse. It’s the best song on the album, capturing the bottled-up tension of a soul in need of passion.

This all-consuming passion drives “Innocence,” and makes for an at-times lyrically fascinating work, one that honors the power of organized sound: “Music so I can exaggerate my pain, and give it a name,” sings Bono on “The Miracle (of Joey Ramone).” Though I’m pretty sure that Joey wouldn’t like this song — too complicated, too many big words — it nonetheless captures the spirit.

It’s tempting to conclude with a cheap shot about the world’s biggest band leveraging itself into your life without permission, something about recipients “getting what they pay for.” It is disconcerting, and anyone bred on the rebellion of punk rock is right to be wary.

What would a teenage Bono think if Yes or Jethro Tull secretly invaded every home in Dublin and dropped their new record on the turntable? I’d wager he’d have a problem with it — and rightly so. And even if such invasion has little to do with the music, it’s difficult to have a pleasant conversation with a friend when you discover she’s snuck into your living room without an invite.