Classic rock bands, in particular those of Iron Maiden's fame and vintage, tend to become static, unchanging figures – reliable nouns among the furious verbs emanating from the music of younger bands. The engagingly creative The Book of Souls, though probably longer than it needs to be, puts Iron Maiden back in the conversation.

There's as much gumption here as in anything they've done, much to thrill die-hard fans, but just as much to challenge their preconceived notions. Iron Maiden pushed themselves when they didn't have to, composing in an entirely different way and emerging with something that builds on their stirring heritage rather than resting on it.

At more than 90 minutes, it's the lengthiest project Iron Maiden have ever attempted, and it concludes with the longest single track they've ever released. Still, The Book of Souls was largely created in the studio, and a sense of visceral engagement runs through the album. They experiment with non-standard tuning in "If Eternity Should Fail"; with free-form jamming during a striking solo segment featuring Adrian Smith, Dave Murray and Janick Gers on "The Red and the Black"; with melancholy ruminations on "Tears of a Clown"; and with a elegiac piano figure in the concluding "Empire of the Clouds."

Also, Iron Maiden sound like a band, not a studio creation. Singer Bruce Dickinson and Smith wrote together for the first time since their joint return in 1999. Murray returned to writing, too, penning the dark and stormy "The Man of Sorrows." That layered complexity, as new perspectives continually bob to the fore, tends to carry listeners as the group dashes through this somewhat overlong and tornadic outburst of creativity.

It's both the risk and the reward with The Book of Souls. By bringing in more voices – founding bassist Steve Harris has only a single solo composition this time out – Iron Maiden sharply widen the album's dimensions but also, importantly, its language. The Book of Souls is all action words and third-act camaraderie, and that feeling of collective rebirth – even if Iron Maiden tend toward run-on sentences here – is often missing on projects like this by lesser legacy groups.

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