The Book of Ruth begins by highlighting the Judges theme of Israel needing a king and exploring the misery and emptiness a singular family might experience during these dark times.
This is not simply a love story.
It's a story about God and how he restores those who look to him with hope. It's about God's covenant faithfulness and it contributes to the overall covenant storyline that unifies the entire Bible. The author has gone to great care to honor Ruth, Naomi, and Boaz through the development of their characters in the story.
They are character studies of how God works in mundane, everyday events in the lives of his people (and what human covenant faithfulness looks like in return).