There is a bit of lewd sex in this story. Naomi
wants her daughter-in-law Ruth to get married, so she tells Ruth to sexually
seduce a man, which she obediently does.
This is a fictional work of literature with a
very important message, so important that it ended up in the Hebrew Cannon of
Scripture and later the Old Testament of the Bible. It is a piece of protest
literature, protesting the current belief of the Jews that only pure 100% Jews
with zero non-jewish ancestors were the chosen ones, and anyone else were
specifically the unchosen ones. The Jews at the time were practising racial
clensing, exiling anyone who was not a 100% pure Jew. It caused great
unhappiness throughout the community as many were sent away due to their
racial impurity. (In a similar way, Hitler claimed racial superiority for the
Aryans, of which he said the Germans were the highest form. As the master
race, they were told, they had the right to dominate all nations they
subjected.) Hence an anonymous person wrote the book of Ruth.
See Commentary on the book of Jonah for a thorough description.
At the end of this story we find that King David himself was not a full-blooded Jew.
His great-grandmother was a Moabite woman named Ruth. David himself would have been
purged by the laws under which the Jewish state was then operating.
Other "books of protest" in the Bible are Job and Jonah.