Deuteronomy is the last book about Moses. It is in the Old Testament part of the Bible.
The Book of Deuteronomy contains the instructions that Moses gave to the people, just before his death. He reminded them about the things that happened in the desert. He taught them God's law. He encouraged them to obey God. Then, God would help them; and good things would happen. But if they did not obey God, they would suffer (Deuteronomy 28).
Moses was the greatest prophet (holy man) in the Old Testament. But God did not allow Moses to lead the people into Israel. Moses appointed Joshua to lead the people after Moses' death.