American Idiot was a rarity of the 21st century: a bona fide four-quadrant hit, earning critical and commercial respect, roping in new fans young and old alike.

It was so big it turned Green Day into something it had never been before -- respected, serious rockers, something they were never considered during their first flight of success with Dookie.

Back then, they were clearly (and proudly) slacker rebels with a natural gift for a pop hook, but American Idiot was a big album with big ideas, a political rock opera in an era devoid of both protest rock and wild ambition, so its success was a surprise.

It also ratcheted up high expectations for its successor, and Green Day consciously plays toward those expectations on 2009's 21st Century Breakdown, another political rock opera that isn't an explicit sequel but could easily be mistaken for one, especially as its narrative follows a young couple through the wilderness of modern urban America.

Heady stuff, but like the best rock operas, the concept doesn't get in the way of the music, which is a bit of an accomplishment because 21st Century Breakdown leaves behind the punchy '60s Who fascination for Queen and '70s Who, giving this more than its share of pomp and circumstance.

Then again, puffed-up protest is kind of the point of 21st Century Breakdown: it's meant to be taken seriously, so it's not entirely surprising that Green Day fall into many of the same pompous tarpits as their heroes, ratcheting up the stately pianos, vocal harmonies, repeated musical motifs, doubled and tripled guitars, and synthesized effects that substitute for strings, then adding some orchestras for good measure.

It would all sound cluttered, even turgid, if it weren't for Green Day's unerring knack for writing muscular pop and natural inclination to run clean and lean, letting only one song run over five minutes and never letting the arrangements overshadow the song.

Although Green Day's other natural gift, that for impish irreverent humor, is missed -- they left it all behind on their 2008 garage rock side project Foxboro Hot Tubs -- the band manages to have 21st Century Breakdown work on a grand scale without losing either their punk or pop roots, which makes the album not only a sequel to American Idiot, but its equal.