The resulting music featured an eclectic fusion of styles, including alternative rock, soul, and jazz-rock, while Ndegéocello's spiritually complex and ambiguous lyrics spoke of romantic love and loneliness, among other themes.

"[1] With Icelandic audio engineer S. Husky Höskulds,[2] Ndegéocello proceeded to record the album in seven days, backed by a band that featured guitarist Chris Bruce, keyboardist Keefus Ciancia, and drummer Deantoni Parks.

[1] Their instruments were recorded live without digital post-production, which Ben Ratliff of The New York Times said contributed to the music's raw and organic sound.

[4] Ndegéocello performed here in what Nick Coleman of The Independent called "the alt-rock idiom",[5] while Slant Magazine's Matthew Cole regarded it as an R&B record that utilized textures from experimental rock and electronica.

The main theme of Devil's Halo was identified by City Pages critic Rick Mason as the treachery of love and its bitter effects.

[8] In Jurek's opinion, "romance, substance abuse, and one woman speaking candidly to another are themes in this musical meditation on bliss, lust, loneliness, and emotional wreckage".

[2] musicOMH journalist Andrew Burgess described the record's content as "achingly sensual and brutally violent",[11] while Seattle Weekly's Saby Reyes-Kulkami said "isolation—even more than the sexual charge the songs exude—serves as the linchpin that pushes her narrators to strive for connection in the first place.

"[12] While the music covered styles ranging from pop and "progressive quiet storm" to "light" avant-garde, The Huffington Post's Mike Ragogna believed the subject matter had a more "low key/high concept" quality expressed through terse lyrics, sonic experiments, and character studies such as "Lola" and "White Girl".

[21] Reviewing the album for Billboard, Gary Graff said it "neatly straddles a line between challenging and accessible", featuring some of Ndegéocello's strongest compositions yet.

[2] Tyler Lewis of PopMatters hailed Devil's Halo as the singer-songwriter's most consistent and "emotionally potent work" since 1999's Bitter while adding that this album featured "a greater sense of perspective of life's realities".

[17] Salon journalist Heather Havrilesky said "like a world-weary muse, Ndegéocello taps into something rich and melancholy at the sludgy bottom of our hearts" while possessing a "mellow depth" in her singing.

[14] In a less enthusiastic review, Andy Gill of The Independent believed the eclectic style on Devil's Halo sounded muddled: "The songs seem to bleed into one another, with too much pointlessly flashy playing leading to polite jazz-rock hell.