You hold out your plastic, hollow pumpkin, jiggling around the mix of euphemistically labeled “fun size” chocolate bars and lollipops. What new delight will this neighbor drop in the pumpkin? A normal-sized candy bar? A bag of Skittles? Bloc Party’s newest album, “A Weekend in the City,” is like a home-made caramel apple from the mildly health-conscious neighbor. It is unfamiliar combination: the core of Bloc Party’s earnestness and post-punk indie rock separated by a mammoth, organic apple of seriousness. The treat’s initial weight inspires dismay, and your mother adds insult to injury by saying you can’t eat it because it’s not wrapped. But after sneaking the apple up to your room and indulging in it, the initial feeling of distress gives way to a bittersweet enjoyment.

“A Weekend in the City,” Bloc Party’s second studio album, is not a sequel to the first album. The albums share the same band, but “A Weekend in the City” channels some of the Britney Spears “not-a-girl-not-yet-a-woman” rebellion: The songs are slower, and the discussion of lead singer Kele Okereke’s personal life more political.

Bloc Party has been chugging from the indie keg filled with, “We are a serious band, singing about weighty issues!” that’s been quaffed by bands like Of Montreal and The Mountain Goats in the past couple of years. Okereke croons about the effect of the 2005 London bombings, concern over the state of race in Britain, and, as he came out in January, his homosexuality. So basically, “A Weekend in the City” is Okereke’s way of declaring he is a politically aware, New-York-Times-reading college freshman. Bloc Party have taken the serious angle before: On “Silent Alarm,” they acted as sort of rock philosophers. It is not in their predilection for the serious, indie keg that the fault lies.

Problems arise, instead, because on “A Weekend in the City,” form has followed function too far. The lyrics are generally just good, as opposed to excellent, so having the music mirror the content comes off to mixed effect. While the aural aesthetic of an album reflecting its content is not a sin, in the case of “A Weekend in the City,” Bloc Party no longer rocks; the album is loud, but it drags. The band’s efforts to show their worldliness, however genuine that worldiness may be, veer into the self-indulgent, with blasé lines like, “I am handed a pill, / and I swallow with complete disdain.”

The moments when the band truly shines are when they stick with the simple, as in “Hunting for Witches” (the track about the London bombings). The song is straightforward and inspires jerky swaying in the listener with its constantly changing stylistic movements. It is a prime example of what the rest of the album could have achieved, with the incongruity of an upbeat tempo and dark subject. Forgoing convoluted metaphors, lyrics like “I want an ordinary man with ordinary desires,” matter-of-factly convey the feeling of alienation that pervades the entire album, from feeling like a stranger in one’s own country to being a stranger in one’s own body.

In the end, Bloc Party maintains its crunchy, sharp core, but the album could have used a little less apple and a little more caramel.