Several years ago in 2007, I put together a bibliography of commentaries on Baruch on this blog. A handful of new work has appeared since then that it is worth listing here. Unfortunately, there is still a dearth of publication on the deuterocanonical book of Baruch, but it is worth cobbling together what has been done. Hopefully, more will be written! The book of Baruch as normally presented in a Catholic Bible includes the Epistle of Jeremiah as the sixth chapter.
New Commentaries on Baruch
Adams, Sean A. Baruch and the Epistle of Jeremiah: A Commentary Based on the Texts in Codex Vaticanus. Septuagint Commentary. Brill, 2014. (Although I haven’t seen it yet, this looks like the most promising, most comprehensive recent work. It claims to be the first English language commentary.)
Hill, Robert Charles, trans. Theodoret of Cyrus: Commentaries on the Prophets. Vol. I. Holy Cross Orthodox Press, 2007. (This includes commentaries on Jeremiah, Baruch and Lamentations.)
Viviano, Pauline. Jeremiah, Baruch. New Collegeville Bible Commentary, vol. 14. Collegeville, MN: Liturgical Press, 2013. (This book includes about 20 pages on Baruch: a 2-page introduction and then the text of Baruch with commentary.)
Wacker, Marie-Theres. Baruch and the Letter of Jeremiah. Wisdom Commentary. Michael Glazier, 2016.