He played college football for the Notre Dame Fighting Irish where his .903 winning percentage (30-3) is second in school history to three-time national champ Johnny Lujack's .932 in the 1940s.

[1] After Notre Dame, Book was selected by the New Orleans Saints in the fourth round of the 2021 NFL draft.

He sat behind starters Malik Zaire and DeShone Kizer in addition to primary backup Brandon Wimbush.

[5] After a pair of slim home victories over unranked opponents the Ball State Cardinals and the Vanderbilt Commodores in 2018, Book was chosen as the starter over Wimbush for a road game against the Wake Forest Demon Deacons.

[citation needed] On December 29, 2019, Book announced via Instagram that he would be returning to Notre Dame for a fifth season as a redshirt senior.

[15] He helped lead Notre Dame to an appearance in the College Football Playoff, where they eventually lost to the Alabama Crimson Tide in the Semifinal Round in the Rose Bowl.

[20] On December 23, 2021, he was named that week's starting quarterback after Taysom Hill and Trevor Siemian were placed on the reserve/COVID-19 list.

[28] On December 26, 2024, with starter Jalen Hurts and backup Kenny Pickett dealing with injuries, the Philadelphia Eagles signed Book to their practice squad.