You've more than likely heard that the Bible has been changed. This claim is more often presented by Muslims, who are, of course, motivated by the fact their Qur'an affirms our Bible, but our Bible doesn't affirm their Qur'an. But Muslims aren't the only ones who claim Bible corruption. Many atheists, of course motivated by a desire to attribute the entire Bible to mankind, assert that the Bible has been changed repeatedly throughout history.
According to these atheists, the Bible has been re-written, translated, edited, re-translated, and changed again repeatedly for the past 2,000 years, to the extent where we have no idea what the original manuscripts actually said. None of this is helped by the books that were taken out or added in over time.
And it's not hard to "prove" this. Much like with all conspiracy theories, there are certain facts which can be stretched to give the impression that the history of Bible transmission is messier than a two year old with a sharpie. However, when you apply a little more critical thought than said two year old, it soon becomes apparent that the myth of Bible corruption just doesn't hold water.
The first, and perhaps most obvious point to prove this is Jesus' supposed failed apocalyptic prophecies. Of course, I do not grant the atheist interpretation that Jesus actually said He would return before His generation would pass away. But if you both insist on taking that interpretation, while simultaneously suggesting the Church edits the Bible according to our desires, why would we leave that part in? It would have been quite obvious, within one generation, that Jesus was not, in fact, coming back yet. And of course, when you combine that with similar conspiracy theories about when the Bible was written, one would have to ask why such things were added in the first place...
You see, then, how atheists can barely keep a consistent narrative. But we don't need to point out holes in their narrative. We can play their game and point out that there is no evidence. In fact, ironically, while there is no evidence that the Bible has been corrupted, there is evidence that there were failed attempts to corrupt it.
We can say these attempts failed because of the embarrassment of riches we have. Obviously, attempting to corrupt a single document does not corrupt other versions of the same document. So, suppose you have 30 copies of the Gospel of John; 10 in Israel, 10 in Egypt, and 10 in Babylon. What you do to the 10 copies in Israel does not affect the 20 in the other two regions. Thus, if you corrupt 10 copies of John's Gospel, John's Gospel not only still exists, but it exists to an extent where the corruption can be spotted.
In reality, we have far more than just 30 extant copies of the Gospel of John. Furthermore, those copies do contain textual variants. However, while unbelievers will act as if these variants give umpteen different versions of the Christian faith, in reality, there are no doctrine-altering variants. In fact, most of the variants are things like spelling errors, accidentally repeated or skipped words, inverted words (e.g. "Christ Jesus" instead of "Jesus Christ"), and other easily spotted differences that cannot be realistically called corruption.
In the interest of transparency, there are some variants, such as the longer ending of Mark, that could be considered substantial. I'm not going to be discussing those here in any great depth, but I thought it would be worth footnoting. Suffice to say for now, these variants do not alter doctrine. If you keep them in Scripture, or take them out, the Christian faith remains the same. Furthermore, while I do not intend to discuss it here, there has been much discussion on it throughout history. Christians are not shy about it by any means.
As for adding and removing works, this is another example of failed attempts at corruption. Ultimately, with few exceptions, all Christian and pseudo-Christian groups throughout history have accepted a similar New Testament canon. The main disputes were over the smaller, later books (1 John - Revelation), which actually shows critical thought on the part of the churches who rejected them. In their eyes, it was better to sideline a work that did come from God than to accept a false work that came from a false prophet. A church that is so resistant to corruption is obviously not going to allow their book to be corrupted.
But ultimately, even with these smaller disputes, we see roughly the same New Testament canon. The oldest canonical lists list these books, and no others. The oldest commentaries, similarly, note these books, and no others. The so called Church "Fathers" refer to these books as Scripture, and no others.
The main disputes, then, are about the Old Testament. Here, we do find some dispute, mainly because of Catholic and Orthodox attempts to add books to the canon that are not Scripture. It is worth noting that even these groups refer to the extra books as Deuterocanonical, or Apocryphal. That is, one way or another, they admit a distinction between the Old Testament canon, and the added books. This is likely because the so-called "Protestant" canon is almost identical to the Jewish canon. To be clear, the Jews both ordered and divided them differently. But the same books in our canon are found in the Jewish canon.
What we see, then, is that this whole thing is an issue of scholarship, not intentional corruption. This, atheists cannot reasonably object to. See, if Christianity is true, then Scripture is Scripture, and we can only recognise it. Therefore, the infamous book of Enoch, for example, was not "taken out" as a matter of convenience, it never belonged there in the first place. Neither do books like Judith and Tobit, which were not inspired by God, and were put in by the Catholic Church as an attempt to spite Luther. But if Christianity was not true, then there would actually be no canon in the first place. Thus, you can't look at certain books and say "this belongs there, the Church took it out" etc. Therefore, whether you believe the Bible as we have it or not, Apocryphal books cannot be a valid argument for corruption.
And there are no valid arguments for corruption, because in spite of all the fanciful fairy tales out there about this shadowy Church who apparently have the power to change every word of every manuscript with the flick of a magic wand, we just have too many ancient manuscripts for the myth to hold water. Even skeptical scholars will admit that we know, with 99% certainty, what the Bible originally said. In other words, the main problem Christians face today isn't 2,000 years of corruption, but 500 years of translation into an ever-changing tongue. This, of course, is another topic for another day.
The Bible corruption myth is one of many failed arguments against the Bible, spread by sinful and ignorant men. But there is salvation for such men. Because the Bible is not corrupt, we know the message the prophets and Apostles preached by Holy guidance. Specifically, they taught that all men are sinners, worthy of the everlasting wrath of the Living God, against whom they have rebelled. However, in His love for them, He sent His Son to live a perfect life as a man, and, ultimately, die on a cross. The uncorrupted Scripture specifically tells us "For He made Him who knew no sin to be sin for us, that we might become the righteousness of God in Him." (1 Corinthians 5:21).
This, in effect, means those who confess Jesus as the risen Lord "swap verdicts". We, who are guilty, may be rewarded with eternal life, because Christ, who is righteous, suffered the full penalty for sin.