http://en.wikipedia.org/wiki/Development_of_the_Old_Testament_canon
with a link to:
http://en.wikipedia.org/wiki/Pseudepigrapha
Basically, Luther agreed with the Jews (who asserted 'cessation of inspiration' because they were used so successfully by Christians to convert Jews) and he dropped them from his translation. His primary initial reasoning was that they supported doctrines, in whole or in part, that he didn't agree with. I personally don't think much of Luther's argument against these OT books due to the wealth of prophesies about Christ in them. It's at least worth noting that Luther also wanted to drop Hebrews, James, Jude, and Revelation, from the NT.
The arguments over whether he was justified in doing so will never end and you can get into as scholarly or as heated a debate (even heated and scholarly debates) over the matter as you like at the drop of a hat. Calvin, like Luther, had his own opinions of what should be included in the Bible and is worth looking into if you're going to pursue why the canon has changed since Christ. Given that He didn't mention anything that needed to be thrown out of the Bible in use while he was on earth, I actually don't understand arguments over the canon. It's too much like rolling your own like a lot of cults do for me to be comfortable with not just sticking to what was in the Septuagint (which I can never spell without checking first).
If you want to do further research it’s tough to find something without an agenda. I think just downloading the following book from the Google thing is a good start because it’s exhaustive enough without much of an agenda (as I recall) and can be very useful for other things as well. Especially for seeing how the usage of words has changed since 1910.
“The popular and critical Bible encyclopædia and Scriptural dictionary” - Herbert Lockwood Willett
Regards
I still find it interesting that the original KJV Bible included these deuterocanonical ( Apocrypha) books and inserted them between the OT and NT.
It's also interesting that, e.g., in the modern Jewish Study Bible (shown @ Amazon.com) the TOC doesn't show the inclusion of any of these books, when clearly they were topical stories of the mainly Jewish, pre-Christian, times and time period.
I have a book called the "First Seven Ecumenical Councils", i guess I should dust it off and read it.