STRUCTURE OF THE BOOK
The structure of the Psalms, is similar to the Pentateuch, which is the Book of the Law, or the Five Books of Moses.
The Book of Psalms, is arranged, or separated, into five books:
BOOK ONE -- Psalms 1-41
BOOK TWO -- Psalms 42-72
BOOK THREE -- Psalms 73-89
BOOK FOUR -- Psalms 90-106
BOOK FIVE -- Psalms 107-150
Each book concludes with a doxology, or a praise, to God, usually found within the last verse, or two, of each Psalm. In the case of Book Five, Psalm 150, in its entirety, is a "concluding" doxology.
The reason for this arrangement of the Book of Psalms, is not clear. Most likely, it had something to do with the use of the Psalms in the praise of God, during the temple worship. Books One and Two, are primarily composed of Davidic Psalms. Book Three, includes Psalms of Asaph, and the sons of Korah. Books Four and Five, include anonymous Psalms, along with those of David and others.
CATEGORIES OF THE PSALMS
The Psalms are broken down into different categories. Many Psalms can be categorized by their themes. For example, the "Royal" Psalms emphasize "God, as King," through the use of the phrase, "the Lord reigns." These Psalms speak of His rule as Creator, Savior of Israel, and as "the coming One."
The "Zion" Psalms, focus on Jerusalem, using its endearing name, "Zion." These Psalms rhapsodize on the city, as God's choice for the site of the Holy Temple, the place for true worship of His name.
The "Penitential" Psalms, are those in which the psalmist confesses sin to the Lord, asks for forgiveness, and then praises the Lord for the renewed relationship, which God's forgiveness provides, e.g., Psalm 51.
The "Wisdom" Psalms, focus on some of the same issues, which we find in the Book of Proverbs. These Psalms present a sharp contrast, between the righteous and the wicked. They address God's blessings and cursings, and often focus on righteous living.
A subcategory of the "Wisdom" Psalms, are the "Torah" Psalms, or poems, which focus on the beauty, truth, and sufficiency of the law of God.
Some of the most troubling Psalms, are those that contain prayers asking God to curse the wicked. These are called the "Imprecatory" Psalms. These Psalms are sometimes thought to conflict with the sentiment of the Gospels, but they actually reflect God's abhorrence of evil.
In contrast, are the joyful, and prophetic "Passover" Psalms, Psalms 113-118. These are the Psalms that were sung at the beginning of the Passover, and were called the "Egyptian Hallel." Psalms 113-115 were sung at the temple, during the slaying of the animals. Psalms 116-117, were sung during the meal, and at the end, Psalm 118. These Psalms are a remarkable celebration of the great acts of the Lord, in delivering His people from Egypt. They point forward to the deliverance that would come through the Savior, Jesus.
A final group of Psalms, is clustered at the end of the book, and are called the "Hallel" Psalms. These Psalms focused on the exodus from Egypt. They praise God for His character, and for His saving work.
The last category, is the "Lament" Psalms.