"[9][10] Drummer Danny Carey operated many of the sound effects on the interlude tracks on the album using electronic drums called Mandalas.

10,000 Days has a heavier sound than its predecessor, largely because of the influence of avant-garde metal band Fantômas, who toured with Tool before the writing process.

"[12] The compact disc packaging for 10,000 Days consists of a thick cardboard-bound booklet partly covered by a flap holding a pair of stereoscopic eyeglasses, which can be used to view a series of images inside.

Alex Grey, who created a majority of the album art for Lateralus and its accompanying video "Parabola," reprised his role for 10,000 Days.

The CD face itself is decorated with stylized eyes, arranged in a seemingly logarithmic spiral toward the center (adapted from a previous Alex Grey painting, "Collective Vision").

"[15] In an interview, Alex Grey, who worked on the illustrations for the 10,000 Days and Lateralus covers, said that many of his artworks for Tool have been based on and influenced by the visionary journeys of a brew called ayahuasca.

[24] Rob Theakston of AllMusic wrote: "It's not only a step forward for the band, but a re-embracing of the epic-length rock songs found at the roots of early heavy metal.

"[27] Alternative Press magazine wrote: "As with everything in Tool's oeuvre, 10,000 Days packs enough beauty, heartache and triumph that it will be dissected, studied and envied by younger bands for years to come.

"[24] Evan Serpick of Rolling Stone stated that on the album, the band "maintains a level of craftsmanship and virtuosity unparalleled in metal.

"[32] Nevertheless, Adrien Begrand of PopMatters stated: "Stupendously packaged, the music robustly mixed and often achieving new levels of bleak beauty, 10,000 Days is too strong a work to call a disappointment, but the constant need to fill out a CD to 75-80 minutes is threatening to become the band's undoing.

"[31] Jess Harvell of Pitchfork Media was critical in his assessment of the album: "Rather than delving further into experimentation or exploring their strengths, Tool have made an...A Perfect Circle record.