Should Christians Keep Old Testament Laws?

Some Christians feel that they should keep Old Testament laws such as the seventh-day Sabbath and avoiding "unclean" meats. The articles in this e-book collection address that, starting with the point that yes, Christians should obey God -- but are the Old Testament laws the laws that we should obey? The Old Covenant is obsolete, and is not a valid source of laws. The example of circumcision shows that God-given laws can be, depending on how you look at it, either swept aside or kept in the spirit, not in the letter.