With over 600 references, "Why Protestant Bibles are smaller" defends the Protestant Old Testament canon using mostly Catholic resources including the Vatican, EWTN, Catholic Answers, and quotations from contemporary Catholic authors like Gary Michuta ("Why Catholic Bibles Are Bigger"), Jimmy Akin ("The Fathers Know Best"), and Trent Horn ("Why We're Catholic"). It utilizes the New Testament to demonstrate Jesus, His disciples, and the New Testament writers espoused to the books of the Protestant Old Testament. Using Christian and Jewish sources from antiquity, such as Eusebius' The Church History, it explains why the canonical lists from early church fathers, early church councils, and the books in the Septuagint, Vulgate, Douay-Rheims, the Dead Sea Scrolls, and even Popes and Cardinals were not identical, and what Jesus, His disciples, and the first century church actually believed about the canon. It includes comments from former Catholics and Eastern Orthodox on the authority of the Protestant Old Testament. It lists nearly 300 specific phrases used in the New Testament to describe Old Testament books, which are only found in the Protestant Old Testament. It concludes with examples of errors and contradictions in the books from the Catholic Old Testament to demonstrate those "extra books" are not "God-breathed" Scripture. This book assures the reader the Protestant Bible contains the complete Inspired Christian canon, which is why Protestant Bibles are smaller.