The Old Testament contains 39 books organized into five categories: the Pentateuch (Law), Historical Books, Poetic Books, Major Prophets, and Minor Prophets. Each book is available as a PDF for reading and study.
Pentateuch
5 BooksThe Law of Moses - Genesis, Exodus, Leviticus, Numbers, Deuteronomy
Historical Books
12 BooksJoshua through Esther - The history of Israel and God's people
Poetic Books
5 BooksJob, Psalms, Proverbs, Ecclesiastes, Song of Solomon - Wisdom literature
Major Prophets
5 BooksIsaiah, Jeremiah, Lamentations, Ezekiel, Daniel - Extended prophetic works
Minor Prophets
12 BooksHosea through Malachi - Shorter prophetic books with powerful messages
New Testament
27 BooksMatthew through Revelation - The life of Christ and the early church