General Rules:
* Capitalize the first letter of each book title.
* Capitalize "The" only if it is part of the official title.
* Use the same capitalization used in the specific Bible translation you're using. Different translations may have slight variations in capitalization, especially for shorter books.
Examples:
* Old Testament: Genesis, Exodus, Leviticus, Numbers, Deuteronomy, Joshua, Judges, Ruth, 1 Samuel, 2 Samuel, 1 Kings, 2 Kings, 1 Chronicles, 2 Chronicles, Ezra, Nehemiah, Esther, Job, Psalms, Proverbs, Ecclesiastes, Song of Solomon, Isaiah, Jeremiah, Lamentations, Ezekiel, Daniel, Hosea, Joel, Amos, Obadiah, Jonah, Micah, Nahum, Habakkuk, Zephaniah, Haggai, Zechariah, Malachi
* New Testament: Matthew, Mark, Luke, John, Acts, Romans, 1 Corinthians, 2 Corinthians, Galatians, Ephesians, Philippians, Colossians, 1 Thessalonians, 2 Thessalonians, 1 Timothy, 2 Timothy, Titus, Philemon, Hebrews, James, 1 Peter, 2 Peter, 1 John, 2 John, 3 John, Jude, Revelation
Exceptions:
* The Book of Psalms: "Psalms" is often capitalized to distinguish it from the word "psalms" used to describe any type of song or poem.
* The Song of Solomon: "Song" is sometimes capitalized in some translations.
* The Book of Ruth: "Ruth" is sometimes capitalized, but other translations will use lowercase.
Important Note: If you are unsure about the correct capitalization for a specific book, consult the specific Bible translation you are using.