Verified answer

I'm not sure there are any that fully qualify. "Problem"'s list is the Apocrypha, which is still treated as canon by the Catholics, but it is Old Testament.

Several works that fall into the historical fiction genre might be considered: The Big Fisherman, The Robe, Ben Hur all come to mind, but these never were regarded as equal to the New Testament.

There are several internal references (in the New Testament) to works that simply no longer exist (in any form), but the way they are referenced suggests that they were treated as equal to those which have survived.

Tobit

Judith

Additions to Esther (Vulgate Esther 10:4-16:24)[20]

Wisdom

Sirach (or Ecclesiasticus)

Baruch, including the Letter of Jeremiah (Additions to Jeremiah in the Septuagint)[21]

Additions to Daniel:

Prayer of Azariah and Song of the Three Holy Children (Vulgate Daniel 3:24-90)

Susanna (Vulgate Daniel 13, Septuagint prologue)

Bel and the Dragon (Vulgate Daniel 14, Septuagint epilogue)

1 Maccabees

2 Maccabees

The question is very broad and greatly depends on what one's personal beliefs are; luthern, catholic, protestant etc . .

As for books that were once regarded as virtually equal, none. Based on the timing of such writings, the author, and what religious organization was behind it. For example the roman catholic church had added books to the Bible with unknow authors and acknowledged as uninspired books (Understanding or believing the Bible is the uninspired Word of God) centuries after the Bible which are Apocrypha books. The Apocrypha inculcates doctrines at variance with the Bible, such as prayers for the dead and sinless perfection.:

"And the day following Judas came with his company, to take away the bodies of them that were slain, and to bury them with their kinsmen, in the sepulchers of their fathers. And they found under the coats of the slain some of the donaries of the idols of Jamnia, which the law forbiddeth to the Jews: so that all plainly saw, that for this cause they were slain. Then they all blessed the just judgment of the Lord, who had discovered the things that were hidden. And so betaking themselves to prayers, they besought him, that the sin which had been committed might be forgotten. But the most valiant Judas exhorted the people to keep themselves from sin, forasmuch as they saw before their eyes what had happened, because of the sins of those that were slain. And making a gathering, he sent twelve thousand drachmas of silver to Jerusalem for sacrifice to be offered for the sins of the dead, thinking well and religiously concerning the resurrection, (For if he had not hoped that they that were slain should rise again, it would have seemed superfluous and vain to pray for the dead,) And because he considered that they who had fallen asleep with godliness, had great grace laid up for them. It is therefore a holy and wholesome thought to pray for the dead, that they may be loosed from sins. (2 Maccabees 12:39-46) (Not in Holy Scriptures)

The apocrypha contains offensive materials unbecoming of God's authorship:

Ecclesiasticus 25:19 Any iniquity is insignificant compared to a wife's iniquity.

Ecclesiasticus 25:24 From a woman sin had its beginning. Because of her we all die.

Ecclesiasticus 22:3 It is a disgrace to be the father of an undisciplined, and the birth of a daughter is a loss.

The apocryphal books themselves make reference to what they call the Silent 400 years, where there was no prophets of God to write inspired materials.

And they laid up the stones in the mountain of the temple in a convenient place, till there should come a prophet, and give answer concerning them. (1 Maccabees 4:46)

And there was a great tribulation in Israel, such as was not since the day, that there was no prophet seen in Israel. (1 Maccabees 9:27)

And that the Jews, and their priests, had consented that he should be their prince, and high priest for ever, till there should arise a faithful prophet. (1 Maccabees 14:41)

LOL God stopped talking huh. But all laughs aside, this is what makes it very difficult for none believers to respect much of the Bible because of writings of such nature that don't match any teachings of Christ. Lastly, with all honestly, there are no contradictions in the Bible. However, there are contradictions in the heart of man.

Probably the Didache

Maybe 1 Clement

Shepherd of Hermes

We have no real record of how the New Testament evolved during the second century to assume something like its present form.