Book took a
redshirt his freshman year in 2016 in order to preserve a year of eligibility. He sat behind starters
Malik Zaire and
DeShone Kizer in addition to primary backup
Brandon Wimbush. Book sat behind Wimbush throughout the
2017 season, but on October 7, 2017, he started for an injured Wimbush against the
North Carolina Tar Heels, propelling the Irish to a 33–10 victory. During the
2018 Citrus Bowl, Book came off the bench and led the Irish to a 21–17 victory over the
LSU Tigers. 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. The result was a 56–27 Notre Dame victory, with Book throwing for 325 yards and two touchdowns, and running for three more. Against the #7 ranked
Stanford Cardinal the next week, Book threw for 278 yards and four touchdowns in a 38–17 rout. The Irish continued to move up the rankings under Book, and in week 10, Book threw for two touchdown passes and ran 23 yards for a score in the closing minutes to lead No. 3 Notre Dame to a close 31–21 victory over the
Northwestern Wildcats. Book helped the Irish to finish the regular season 12–0 and earn its first
College Football Playoff berth, although the Irish were defeated by the eventual national champion the
Clemson Tigers in the
2018 Cotton Bowl Classic, 30–3. On September 14, 2019, Book threw for 360 yards and five touchdowns, and also had one rushing touchdown in a 66–14 win over the
New Mexico Lobos. He contributed to the most points scored in a home opener at Notre Dame since 1932. On October 5, 2019, Book threw five touchdowns in the first half against the
Bowling Green Falcons, becoming the first player in Notre Dame history to have five scores in one half. On November 9, 2019, Book threw four touchdown passes in a win against the
Duke Blue Devils. On November 16, 2019, Book threw for 284 yards and five touchdowns against the
Navy Midshipmen, making him the first Notre Dame quarterback in history to have five touchdown passes in three games for one season. On December 29, 2019, Book announced via
Instagram that he would be returning to Notre Dame for a fifth season as a redshirt senior. On December 5, 2020, Book passed
Tom Clements,
Ron Powlus, and
Brady Quinn for most wins as a quarterback in Notre Dame football history with 30 total wins as a starter. His 72 touchdown passes are second all-time in program history. He finished 9th in the Heisman Trophy voting. 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. Book holds school records for wins as a starting QB (30), single-game yards per completion (24.0 against New Mexico in 2019), single-season completion percentage (68.2% in 2018), consecutive pass attempts without an interception (266 in 2020), and lowest interception percentage in a career (1.75%). ==Professional career==