A short, accessible resource with excellent cultural background information is Finding God in the Margins by Carolyn Custis James. Listeners should also check out the chapter on Ruth in A Biblical-Theological Introduction to the Old Testament: The Gospel Promised. Commentaries on Ruth are often combined with commentaries on Judges, as is the case in the Tyndale Old Testament, New American, and NIV Application commentary series. Listeners wanting to go deeper into the theological, literary, and historical aspects of the book should check those volumes out, as well as the commentary by Robert L. Hubbard Jr. in the New International Commentary series. As always, the Bible Project video on Ruth is helpful: https://youtu.be/0h1eoBeR4Jk