The Old Testament has 39 books total, which consist of…

Genesis
Exodus
Leviticus
Numbers
Deuteronomy
Joshua
Judges
Ruth
1st Samuel
2nd Samuel
1st Kings
2nd Kings
1st Chronicles
2nd Chronicles
Ezra
Nehemiah
Tobit
Judith
Esther
1st Maccabees
2nd Maccabees
Job
Psalm
Proverbs
Ecclesiastes
Song of Songs
Wisdom
Sirach
Isaiah
Jeremiah
Lamentations
Baruch
Ezekiel
Daniel
Hosea
Joel
Amos
Obadiah
Jonah
Micah
Nahum
Habakkuk
Zephaniah
Haggai
Zechariah
Malachi

Grouped into 5 Groups

Pentateuch – 5 books
Genesis, Exodus, Leviticus, Numbers, Deuteronomy

Historical Books – 12 books
Joshua, Judges, Ruth, First Samuel, Second Samuel, First Kings, Second Kings,
First Chronicles, Second Chronicles, Ezra, Nehemiah, Esther.

Poetic books– 5 books
Job, Psalms, Proverbs, Ecclesiastes, Song of Solomon

Prophetic books– 17 books
Major Prophets – Isaiah, Jeremiah, Lamentations, Ezekiel, Daniel
Minor Prophets – Hosea, Joel, Amos, Obadiah, Jonah, Micah, Nahum, Habakkuk,
Zephaniah, Haggai, Zechariah, Malachi.