In the protestant bible there are 66 different books which make up the Old and New Testaments. In the Catholic bible and Eastern Orthodox Church there are 73 different books which make up the Old and New Testaments. In the Ethiopian bible there are 81 different books which make up the Old and New Testaments.
The Ethiopian bible has fifteen books not included in the protestant bible. Seven of those fifteen books are included in the Catholic bible, Eastern Orthodox Church bible, and the Oriental Orthodox Church bible. In the protestant bible there are quotes from ten of those fifteen books not included in the protestant bible.
How did these differences come to be?
Here is the short version. In the council of Rome 382 A. D. They canonized (or accepted) the 46 books of the Old Testament and the 27 books of the New Testament to compile the 73 books of the Bible. These 73 books are included in the Catholic bible, Eastern Orthodox Church bible, Oriental Orthodox Church bible, and the Ethiopian Church bible.
Following Martin Luther’s departure from the Catholic Church he began translating the books of the Bible into German. Luther did not consider the “Apocrypha books equal to the Holy Scriptures, but useful and good to read.” These are included in copies of the Luther Bible as intertestamental books between the Old Testament and New Testament and not considered equal with the other 66 books in Luther’s Bible.
Later during the reformation movement of the 16th - 17th centuries groups like Anabaptist, Lutheran, Methodist, Presbyterian, and Reformed Churches (better known as protestant churches) removed seven of the Old Testament books which Luther had termed as deuterocanonical books or Apocrypha books. Which is why protestant bibles only have 66 books (39 Old Testament books and 27 New Testament books) instead of the 73 books originally included.
Should these differences cause us to question the accuracy and reliability of the Bible?
My answer is no. These differences are not differences in meaning or theology. They are not contextual differences. The bible has proven to be reliable and accurate in its history, geography, historical figures, and science. The bible reveals to us a limited understanding of God and his nature. I believe we can accept the trustworthiness of the biblical narrative to reveal to us God and his glorious divine plan to redeem humanity, but also admit there may be some human personality or persuasion included in these Holy Letters.
I believe these differences reveal a truthfulness we would rather just ignore, and that is humanity is not infallible. The church is not infallible. Humanity has always struggled to remain humble. Our egos get in our way, and we begin to think we are right and everyone else is wrong. Each of us have our learned biases, and unfortunately that truth may have influenced what we call the Holy Bible. It has definitely influence Church culture! Why do you think we have so many different denominations? We are infallible.
Here is the good news, God is infallible! And in spite of our egos and brokenness, God was willing and able to use human personality to reveal himself to us. God was able to work through history to unfold his divine plan of redemption. God was able to cause an emperor to call a census, a newlywed couple to travel to Bethlehem, kings to follow a star, at a precise time in history to reveal his son to the world - IMMANUEL!
And while infallible man/woman have penned holy writings I trust God is more than able to inspire and direct the hand that moves the pen.