By Ian Youngs
Music reporter, BBC News
U2 performed their new single Get On Your Boots at the Brit Awards
Five years after their last album and more than 20 since they became the biggest band in the world, the time has come for U2 to reclaim their rock 'n' roll crown.
With a career of almost unparalleled success and acclaim, expectations are high for their new album, No Line on the Horizon. So does it deliver?
Every big band is judged on, and defined by, their biggest tunes.
For U2, The Joshua Tree's opening salvo of Where The Streets Have No Name, I Still Haven't Found What I'm Looking For and With Or Without You put them at the very top of the rock pecking order in 1987.
More recently, they have kept the hits coming coming. Their last album How To Dismantle An Atomic Bomb was led by three big tunes - Vertigo, Sometimes You Can't Make It On Your Own and City Of Blinding Lights.
Its predecessor All That You Can't Leave Behind, in 2000, contained Beautiful Day, Stuck In A Moment You Can't Get Out Of and Elevation.
Those were all stirring, soaring U2 anthems.
This album is a bit different.
The huge, rousing tunes are still there. About half of the new album could be classed as having come from the classic U2 mould - driving rhythms, wide open guitars, impassioned vocals.
But they don't quite scale the heights we have come to expect.
Get On Your Boots, the first single, has been met with a lukewarm response. The guitars sound dirty, not uplifting, and the "sexy boots" refrain is uncharacteristically mundane and ridiculous.
I'll Go Crazy If I Don't Go Crazy Tonight, Magnificent and Stand Up Comedy are the closest things to U2 epics. But they lack the simple power of the group's grand anthems.
Now for the good news.
The other side of the album sees a different U2 take over - a band that are expanding their vision, tilting their ambitions and letting their instincts for melody and musicianship deliver some stunning songs.
Some of these tunes are mellow and warm, some are stripped back and personal.
Some take the trademark U2 ingredients of passion and power but play with melody and structure in a way that makes them stimulating and satisfying, even if they swerve to avoid a soaring chorus.
No Line On the Horizon, the title track, builds on subtly shuffling guitars and drums, and is given impetus by Bono's simple, repeated verses that are followed by flourishing wails.
Moment of Surrender, a seven-and-a-half minute slow burner, is long but never dull. Upon laid-back beats are layered strings, an organ and a gospel backing, before The Edge's quivering guitar sends it into the dreamy, dusty distance. It is arguably the outstanding track.
Unknown Caller, clocking in at six minutes, starts with sun-blushed chimes and flutters, and is built around a chanted chorus, as some desert drums, a familiar panoramic guitar and some wandering "woahs" join in.
Cedars of Lebanon, the closing track, is more bare, but no less compelling, with reflective vocals on top of brushed beats and plaintive twanging.
This is the sound of a band at ease with themselves, exploring their possibilities. They have been aided by producers Brian Eno and Danny Lanois, who also have co-writing credits this time.
When they try to do classic, bombastic U2, they fall short. The absence of stadium-sized sing-a-long choruses could see some write them off.
They may have turned a corner, but they are now pointing in a more interesting direction.