To explore what books school principals are reading and to determine how those books influence principals’ professional practices. A comprehensive literature review was cross-referenced with in-depth interview (IDI) results from 20 currently practising building principals at both the elementary and secondary levels. This narrative case study is a census in which 20 of the 24 principals in a rural/suburban school district during the 2022–2023 school year participated in the IDI process utilising a pre-interview checklist and a semi-structured interview protocol. The data were analysed according to Saldaña’s (The coding manual for qualitative researchers (4th ed.). Sage Publications 2021) Codes to Theory model. We first explored the book recommendations of school principals, which included 122 unique book titles and 204 total recommendations. We then examined how books influence school principals’ professional practices through the lens of professional learning, including self-study, principal professional development (PPD), book studies, and shared books. Three conclusions emerged from this research: 1) books inform professional practices; 2) what gets read gets implemented; and 3) professional learning permeates many other influences on professional practices. This study holds significant implications for all PPD supervisors and all those who facilitate professional learning for principals at both the elementary and secondary levels.