[citation needed] In April 2011, Adams released an EP, Class Mythology, featuring four unreleased tracks recorded for Cardinology.

"[20] Billboard also gave it a favorable review and said, "Musically, the band works up a handsome country rock sound with shades of the Rolling Stones and Wilco throughout, making room for swagger ('Fix It,' 'Magick') and sentimentality ('Natural Ghost,' 'Evergreen') in equal measure.

"[21] Similarly, The Boston Globe gave it a favorable review and said, "If only a few of the tracks rise to the greatest heights of which Adams is capable--like the poignant closing salute to sobriety, 'Stop'--the rest remain impressive pictures of craftsmanship.

Club gave it a B and stated: "Even at his slightest--and Cardinology is pretty slight--Adams always turns out likeable ear candy.

"[24] Tiny Mix Tapes gave it three-and-a-half stars out of five and said: "The new attention to cleanly produced and perfectly played and arranged backdrops function as both a blessing and a curse.

"[25] Other reviews are average or mixed: Uncut gave it a score of three stars out of five and said it ultimately "serves as another minor indictment of Adams’ famously lackadaisical internal editor.

"[1] Under the Radar also gave it five stars out of ten and said that "if you’ve always wanted to hear U2’s frontman lead a hook-filled classic country/rock band, Cardinology is for you.

"[1] Slant Magazine gave the album two-and-a-half stars and stated that "too often Cardinology seems content to float along on an oily sea of good feelings and bad attitude.