Why the Order of the Books Simply put, the Old Testament is arraigned according to the Septuagint Greek version, departing from the Hebrew Jewish order. Notice that Jesus referred to the Hebrew Bible order twice when He spoke of the (a) "Law, Prophets, and Writings," (Luke 24:44) and (b) "upon you may come all the righteous blood shed upon the Earth, from the blood of righteous Abel unto the blood of Zacharias...whom you slew between the Temple and the altar." (Matthew 23:35; the Hebrew Bible began with Genesis and ended with the Books of Chronicles.)
{Following the lead of the Palestinian Canon, the Deuterocanonical and Apocryphal writings were left out of the Old Testament Christian canon. But some religions have placed them "between" the Testaments as profitable and inspirational reading.}
The Modern Bible differs some from the LXX in the order of the prophets. The "Major Prophets" were moved from the end to the beginning of the prophetic section. And one or two of the Minor Prophets have a different order. So now the prophetic section goes from Isaiah unto Malachi.
Instead of the groupings of the Old Testament books being "the Law, Prophets, and Writings," the Christian Old Testament has:
The Torah (5 books of Moses)
the History books (Joshua to Esther)
the Wisdom literature (Job to Song of Solomon)
The Major Prophets (Isaiah to Daniel)
The Minor Prophets (Hosea to Malachi).
The New Testament was arraigned by Martin Luther according to the amount of emphasis that was placed on Jesus within the books. Of course, the New Testament would start with the four Biographies of Jesus (Gospels). And the ending epistles deal to a large extent with the Church community.
Martin Luther considered four books to be disputable as far as the canon went (Jude Hebrews, James, Revelation), so he placed them at the back of the New Testament. He may have done this on doctrinal grounds; they are now accepted and placed in the New Testament canon, which is grouped as:
The Gospels of the Evangelists
History (Acts of the Apostles)
Episles of the Apostles (Romans to Philemon)
A theological Essay (Hebrews)
Various Epistles (James to Jude)
an Apocalypse (Revelation of John)
Chronology Since the books of the Bible are not in chronological order, one must read Introductions to the books in a "Study Bible" for information about the author, location, and year of writing.
The reason why the books of the Bible are in their present order is largely due to the influence of the Greek Septuagint translation of the Hebrew Bible (LXX), and to Martin Luther's research.