The book of psalms is split into five smaller books; they are significant because they reflect the themes of the Pentateuch, the first five books of the Bible.
Book 1 (psalms 1-41), is about man, and they refer back to Genesis and the creation of man.
Book 2 (psalms 42-72) is about deliverance which neatly matches the book of Exodus and the Israelites’ escape from Egypt.
Book 3 (psalms 73-89) is about the sanctuary, which ties in with the book of Leviticus which is chiefly concerned with the priestly duties.
Book 4 (psalms 90-106) is about conflict, a subject which is dealt with extensively in Numbers.
The final book of psams reflects the final book of the Pentateuch, and is concerned with the God’s Word. Deuteronomy contains the speeches Moses gave to the Israelites concerning what God was teaching them.