The book of the Covenant:

Exo 24:7 BSB Then he took the Book of the Covenant and read it to the people, who replied, “All that the LORD has spoken we will do, and we will be obedient.”

So all the contents of Exodus chapters 20-23 amount to the Book of the Covenant. To be His people, these are the minimum statutes we must keep. There are more detailed laws later on how to keep these first few, but the Ten Commandments were just the opening act to this Covenant at Sinai.