The album was lyrically inspired by the memberships of Bono, the Edge, and Larry Mullen Jr. in a Christian group called the Shalom Fellowship, and consequently it contains spiritual and religious themes.

Their involvement with Shalom Fellowship led them to question the relationship between the Christian faith and the "rock and roll" lifestyle, and threatened to break up the band.

The recording sessions were complicated by Bono's loss of a briefcase containing in-progress lyrics for the new songs, forcing a hurried, improvisational approach to completing the album on time.

[2] In March, on an otherwise successful American leg of the tour, the briefcase of lead vocalist Bono containing in-progress lyrics and musical ideas was lost backstage during a performance at a nightclub in Portland, Oregon.

[3][4] The band had limited time to write new music on tour and in July began a two-month recording session at Windmill Lane Studios largely unprepared,[5] forcing Bono to quickly improvise lyrics.

"Tomorrow", a lament to Bono's mother, who died when he was young, features Uilleann pipes played by Vinnie Kilduff later of In Tua Nua.

October was the start of U2's vision of the music video as an integral part of the band's creative work, as it was released during a time that MTV was first becoming as popular as radio.

It all breathes fire, recovering too from the pair of standouts appearing at the start of each side – 'Gloria' being possibly Their Finest Moment and 'Tomorrow', low and muted, gently oozing emotion".

[23] Adam Sweeting of Melody Maker also wrote a favorable review, saying: "Their whole musical sensibility is shaped by a strong emotional bond to their homeland and its traditions.

He concluded: "Obviously rock doesn't expire just because groups run out of ways to change it... U2, I guess, will continue to 'move' in live performance, but they will only move on the lightest surface.

[25] Jon Pareles of Rolling Stone praised the Edge for his powerful guitar playing, "drenched in echo and glory", but said Bono's vocals were negatively impacted by him taking himself too seriously and that his lyrics were silly and clichéd.

[21] In a retrospective review, Stephen Thomas Erlewine of AllMusic said the band "tries too hard to move forward" on October, with Bono straining to make big statements and the music sounding "too pompous".