The big news surrounding U2's 13th album is its surprise attack. Unexpectedly unleashed at an iPhone unveiling, 'Songs of Innocence' was made available as a free download on iTunes to anyone who wanted it. That's a risky venture no matter how you look at it. With the music industry sinking to all-time lows, it's either the shrewdest or stupidest move ever made by a superstar artist.

U2 are banking -- figuratively now, but you can bet they'll be making money off this somewhere down the line -- on the former.

And you can forgive and excuse their confidence: The 11 songs aren't throwaways. This is a legitimate U2 album, right down to the very seriousness that runs through its stacked grooves. Gimmick aside, 'Songs of Innocence' is no better or worse than any other U2 album of the millennium (not counting the century-starting 'All That You Can't Leave Behind,' a record as powerful and as magnificent as anything they've done). It's a bit bulky, it's a bit overbearing and it runs out of steam before it reaches the end.

But it's also a relatively pomp-free outing that unfolds more seamlessly than the band's last few albums. In that sense, 'Songs of Innocence' is a bit like U2's most recent record, 2009's 'No Line on the Horizon,' but without the overriding self-importance. A roster of producers -- including, most famously, Danger Mouse -- pull it all together with touches of the traditional mixing it up with the modern. There are few curveballs here; like 'No Line on the Horizon,' 'Songs of Innocence' is a U2 album for fans who like U2 best when they sound like U2.

That's not to say they settle into formula. The opening 'The Miracle (Of Joey Ramone)' is all buzzing guitars, distorted vocals and a clickety-clack rhythm that comes off like a futuristic arena shaker that splits the difference between 'Achtung Baby' and Danger Mouse's work with the Black Keys. But on the very next song, 'Every Breaking Wave,' they recycle 'With or Without You''s pulsating bass and ominous soundscape for the album's most familiar-sounding track.

And the bulk of 'Songs of Innocence' is like that: Old-school U2 tweaked with just enough modernity to keep them from becoming a nostalgia act. Songs like 'California (There Is No End to Love),' 'Song for Someone' and 'Cedarwood Road' rattle and hum with the best of the band's post-'Leave Behind' numbers, but without history to inform them, they lose some of their might. U2 have gotten to that stage in their career where everything they do will be measured by what they did before. After 13 albums, it's inevitable.

By the time things wind down on the closing song, 'The Troubles' -- a moody, somber duet with Swedish indie-pop singer-songwriter Lykke Li -- you realize that the initial surprise of having a brand new U2 album show up unannounced in your iTunes playlist is the most forward-thinking thing about 'Songs of Innocence.' And it's a reminder that sometimes staying on track is the most reliable, rewarding and safest route.