Hi Gibster,
The laws written in the Book of Leviticus are not all eternal. The Ceremonial Laws which were all about Temple sacrifices and worship are all obsolete because Jesus fulfilled all the sacrifices with his death on the cross. (Hebrews 9:11-15) Also the Temple was destroyed in 70AD making it impossible to keep those laws. However they are still valuable because we can learn a lot about God and spiritual principles from them.
In Leviticus we also have civil laws. They were written for the nation of Israel which was governed by God as a Theocracy. The laws actually showed how kind God was, especially if you compared them with the laws of other nations at the time. They were pretty brutal in those days.
For instance, you could only keep a slave for 6 years and then you had to release him on the 7th year. People offered themselves as slaves to stop themselves starving to death. If a slave liked his owner a lot he could opt to remain his slave for life. The owner of the slave couldn't treat him anyway he saw fit; he had to be considerate. This is a far cry from what we've seen about slavery in more recent histories.
All the civil laws applied to everyone equally; there were not different rules for upperclass people, and different rules for lower class people, as was the case in other societies. There were many laws which provided for poor people.
There were also numerous laws about hygeine. This was thousands of years before our understanding of germs and antispetics. Very useful laws they were.
Again these laws show us Godly principles but we are under no obligation to keep them. Although some are very useful and worth keeping.
Christ is the end of the Law so that there may be righteousness for everyone who believes Romans 10:4
Know that a man is not justified by observing the law, but by faith in Christ Jesus. Galatians 2:16
You who are trying to be justified by the law have been alienated from Christ; you have fallen away from grace Galatians 5:4
If you are led by the Spirit you are not under the Law. Galatians 5:18
We now live under a New Covenant and the only Laws we are obligated to keep are those that have been restated (and often expanded) in the New Testament!
Only the Ten Commandments are truly eternal. God engraved them with his finger on stone tablets. We should try to keep them and the New Testament Law of Christ (see 1 Corinthians 9:21; Galatians 6:2), while remembering that salvation is not by works but it is a gracious, undeserved gift from God. (Ephesians 2:8-9)