Answer
The Book of Baruch is part of what is considered the Apocrypha/Deuterocanonical writings and appears in the Old Testament of Catholic Bibles. Except for some Episcopal or Lutheran Bibles, the Book of Baruch and other books of the Apocrypha do not appear in Protestant Bibles. Apocrypha means “hidden,” and Deuterocanonical means “second-listed.” Books of the Apocrypha were mainly written in the roughly 400 years between the composition of the books in the Old and New Testaments, the so-called intertestamental period. Baruch is one of 12-15 books generally recognized as comprising the Apocrypha.
Controversy surrounds the Apocrypha regarding whether these books are from God or divinely inspired. For example, some biblical scholars point out that Jesus never quoted any verses from the Apocrypha, although He quoted with great frequency from many Old Testament books. Many books of the Apocrypha contain historical or geographical inaccuracies and teach false doctrines (e.g., the Book of Tobit claims good works lead to salvation). Plus, Jewish Scripture never included any of these documents as sacred writings.
In response to the Reformation, the Catholic Church, after centuries of not acknowledging these writings fully, canonized the Apocrypha at the Council of Trent in 1546 in part to provide “biblical” justification for some doctrines not found in originally canonized works, e.g., praying for the dead, purgatory, salvation by almsgiving, etc. It was during the Reformation that doctrinal validity was judged against the principle of sola scriptura (Scripture alone). So, by accepting writings in the Apocrypha that mentioned the above practices not found in original Scripture, the Catholic Church could support its theological position and the validity of these doctrines during this tempestuous time.
The Catholic Church uses Baruch 3:9-38 as part of its Holy Saturday liturgy during Passiontide (Easter Season). This portion of the book, which speaks of obtaining and desiring wisdom, concludes with a verse referencing Christ’s living among us. The Eastern Orthodox Church uses Baruch among its Old Testament readings during Christmas Eve services. Some early Christian theologians quoted from Baruch, including Thomas Aquinas, St. Clement of Alexandria, and St. Hilary of Poitiers.
The Bible records that Baruch was Jeremiah’s secretary, who wrote the prophet’s words on a scroll (Jeremiah 36:4). Within the Book of Baruch, the central themes are Israel’s disobedience to God, God exiling Jews to Babylon due to their behavior, God’s just action, the need to repent and honor and obey God’s Word, and begging for God’s mercy. In the first chapter of Baruch, it is stated that Baruch read this book aloud to Judah’s King Jeconiah (Baruch 1:3). Jeconiah is also mentioned in the Old Testament as someone who did “evil in the eyes of the Lord,” as did his father, Jehoiakim (2 Kings 25:8).
Baruch is considered a prophetic book and was found in the Septuagint and Vulgate Bible. In many versions, the Letter of Jeremiah is added as a sixth chapter. In other versions, however, Baruch concludes with a short, 9-verse fifth chapter.