The book of Ruth as a big departure from the violent chapters prior to it. It shows the love and dedication of Ruth, and also Ruth is part of the genealogy line that eventually is Jesus Christ.
This site lays out three lessons from the book; God’s love for the Gentiles, Divine Providence, and a preview of Christ: https://www.christiancourier.com/articles/1110-lessons-from-the-book-of-ruth
Another passage that describes this book well: “Right now, in the homes of seemingly unimportant people who are living and dying with little public awareness, God may be fully engaged in shaping the future history of the world. God looks deep inside all people. He is taken not by the size of their bank accounts, popularity, authority or intellect, but by the quality of their character, just like He was with Ruth.” https://lifehopeandtruth.com/bible/holy-bible/old-testament/the-writings/the-book-of-ruth/ check out this site for an excellent commentary.