Why Do Different Bibles Include Different Books in the Old Testament?

How many books are there in the Old Testament? This might seem like a fairly straightforward church trivia night question. But actually the answer can vary depending on which Bible you are reading. The Hebrew Bible has 22 or 24 books. Your English Old Testament probably has 39. Roman Catholic Bibles have 46 Old Testament books. Eastern and Russian Orthodox Bibles have even more. I find this discrepancy often comes up in dialogue with atheists and Muslims about the reliability of the Old Testament. Why the difference? …