Check the Foo Fighters' website and you'll be confronted with Dave Grohl's preamble about how this, their fifth studio album, is their most ambitious, effort-intensive, surprising release to date. He's not lying. Any reservations about the Foos dropping a double CD set are assuaged by the fact that these are two very individual albums. The first is hard-pop-rockin', old-school Foo fan-appeasin' music, while the other's a riskier, sensitive "we've matured" all-acoustic album featuring harmonicas, panoramic strings, and - sweet Christ! - a guest appearance by Norah Jones. Surprisingly, it all works. Grohl's voice fares well against the starker backdrop of disc two, and even at their worst the lyrics are unobtrusive and safe. The Foos may be trying to appeal to everyone, but they've managed to pull it off with class.