What is the "Christian" Bible to begin with? Historically, that question is far more difficult to answer than you might suppose. For instance, in 1740, a list of the canonical books compiled in Rome just prior to 200 A.D. was discovered in the Ambrosian Libary in Milan, Italy. Missing from the accepted canon in 200 A.D. were Hebrews, James, 1 Peter and 2 Peter. Only two of John's letters were considered canonical, not three, but we don't know for sure which two. The Apocalypse of Peter and the Wisdom of Solomon, however, were included.
Eusebius of Caesara, one of the most notable Church historians to have ever lived, described (in about 300 A.D.) a canon which included only twenty-seven of the books in today's New Testament. Hebrews, James, and 2 Peter where described as questionable, as were Jude and Revelation. In the fourth century, St. Gregory of Nazianzus continued to reject Revelation and states, "You have all. If there is any any besides these, it is not among the genuine [books]." The canon he set forth was ratified some three centuries later.
The Greek Codex Claromontanus, one of the most significant New Testament manuscripts, contains a list of the canonical books of the fourth century. (The manuscript itself originates in the sixth century, however most scholars believe that the actual list dates back to the Alexandrian Church from two centuries earlier.) That list did not exclude Philippians, 1 and 2 Thessalonians or Hebrews. But guess what? It does include the Epistle of Barnabas and the Shepherd of Hermas.
Other books that are mentioned by name in today's Bibles cannot be found there at all. One example is Paul's epistle to the Laodiceans. Why was it less authoritative than his other epistles? It's mentioned in Colossians 4:16. Obviously, it was considered authoritative at the time it was written. Paul also wrote an additional epistle to the Ephesians and another to the Corinthians. When did his "apostolic authorship" come into question? Jude, too, wrote another epistle. What reason is there to believe it was so unreliable as to have been intentionally omitted from the today's canon? Or maybe it was just lost.
If we go to the Old Testament, there are even more books that are missing. These were written by "Samuel the seer," "Nathan the prophet," "Shemaiah the prophet" and others. 2 Chronicles mentions many of these by name. Why haven't we gotten rid of 2 Chronicles by now, since it references so many prophets whose work was apparently not the word of God after all?