The Bible has not remained unchanged since it was first formed. The Roman Catholic, Orthodox and Protestant denonminations use different formats (ie different make up of books) as well as different translations.
Protestant Bibles contained certain deutrocanonical books until the 1820s.
Roman Catholics recognise seven deutrocanonical books (Tobit, Judith, 1 Maccabees, 2 Maccabees, Wisdom of Solomon, Ecclesiasticus, and Baruch) to be part of the Bible
Some Orthodox Churchs include 3 Maccabees, Psalm 151, 1 Esdras, Odes, Psalms of Solomon, and occasionally 4 Maccabees.
This means that most Protestant divisions have a Bible containing 39 OT books whilst Roman Catholics have an OT of 46 books.
The NT of 27 generally remains fixed, however.
All information taken from:
http://en.wikipedia.org/wiki/The_Bible#The_Old_Testament
http://en.wikipedia.org/wiki/Deuterocanonical_books