The exact books included in the Old Testament vary from Christian tradition to Christian tradition. While all major Christian traditions recognize the books of the Hebrew Tanakh, some also recognize certain other books. For instance, the Ethiopian Orthodox Church recognizes 1 Enoch as a canonical book, whereas other Christian denominations do not.
See Biblical Canon.
The Protestant Old Testament takes a very conservative approach; in most respects, it is identical to the Tanakh, recognizing no Deuterocanonical works. Thus, there are 39 books in the Protestant Old Testament. These are, in order:
Committing all 39 books to memory can be daunting; the following poem may prove a useful mnemonic.
That great Jehovah speaks to us, In Genesis and Exodus, Leviticus and Numbers see, Followed by Deuteronomy, Joshua and Judges sway the land, Ruth gleans sheaves with trembling hand, Samuel and two Kings appear, Whose Chronicles we wondering hear, Ezra and Nehemiah now, Esther, the beauteous mourner show, Job speaks in sighs, David in Psalms, The Proverbs teach to scatter alms, Ecclesiastes then comes on, And the sweet Song of Solomon, Isaiah, Jeremiah then, With Lamentations takes his pen, Ezekiel, Daniel, Hosea's lyres, Swell Joel, Amos, Obadiah, Next Jonah, Micah, Nahum come, And lofty Habbakuk finds room, While Zephaniah Haggai calls, Rapt Zechariah builds his walls, And Malachi, with garments rent, Concludeth the Old Testament.