It's important when reading these books to remember that there are three different kinds of laws in the Old Testament, only one type of which remains valid, the moral law.
The civil laws you find there have no standing because the nation to which the laws were given, ancient Israel, no longer exists, no longer is a theocracy under Yahweh.
The need for ritual/sacrificial law, including things purification rites and dietary rules also has ended. That occurred when Jesus became the final, definitive sacrifice for human sin.
The moral law cannot save us from sin, death, and separation from God because none of us is capable of perfectly keeping it. This is why our salvation depends on Jesus, Who offered His sinless life in sacrifice for our sins, taking the condemnation of death we deserve and Who gives us a share in His resurrection victory over all that separates us from God as a gracious gift we receive by faith in Him. Even our capacity to believe, to trust, in Him is a gift. (Trust doesn't come naturally to self-centered, skeptical sinners.)
But even the archaic civil and ritual laws can show us some things about who and what God values in humanity.
For example, during my quiet time with God today, I read and highlighted this passage:
When you are harvesting in your field and you overlook a sheaf, do not go back to get it. Leave it for the foreigner, the fatherless and the widow, so that the Lord your God may bless you in all the work of your hands. When you beat the olives from your trees, do not go over the branches a second time. Leave what remains for the foreigner, the fatherless and the widow. When you harvest the grapes in your vineyard, do not go over the vines again. Leave what remains for the foreigner, the fatherless and the widow. Remember that you were slaves in Egypt. That is why I command you to do this.
[Ruth, one of my heroes, was a foreign widow forced to glean in ancient Israel at one point. She became the great-grandmother of the nation's greatest king, David.]