Let's begin by acknowledging that none of the autographs of the New Testament books have survived to today. This is not surprising. The papyri (or even parchments) on which they would have been written could not be expected to last long, especially as these particular texts would have been passed around and read with great regularity. The fact is that we don't have the autograph of any such ancient text, biblical or otherwise.
So, the issue with regard to the reliability of any ancient document is not whether or not we have the autographs. The questions are 'How many copies do we have?' and 'How close are they to the date of the original?' So how do the books of the New testament compare (on these criteria) with other ancient manuscripts accepted as reliable?
Caesar wrote Gallic Wars between 100-44 B.C. Ten copies exist today, with the earliest dating to A.D. 900, about 1,000 years after the original.
The Athenian general Thucydides wrote his History of the series of wars between Athens and Sparta between 460 and 400 B.C. There are only 8 extant manuscripts, the earliest dating to A.D. 900, 1,300 years after the autograph.
Tacitus wrote his Annals in about A.D. 100 (at approximately the same time as the last NT book was written). Twenty copies have survived to today, with the earliest coming from A.D. 1100, 1,000 years after the autograph. Historians consider the copies of each of these books as providing reliable evidence for what the originals said.
The New Testament books were written between A.D. 50 and A.D. 100. An astounding 5,366 copies (in the Greek) survive to today. The earliest (a fragment) dates to A.D. 125; whole books are found as early as A.D. 200; most of the New Testament is represented in copies from A.D. 250, and copies containing the entire new Testament date to A.D. 325, only 225 years after the last autograph! The conclusion of scholars in this field is expressed by F.F. Bruce...
There is no body of ancient literature in the world which enjoys such a wealth of good textual attestation as the New Testament.In brief, the fact that we don't possess the originals of the New Testament books is not a barrier to our understanding what those originals said. Nonetheless, the copies we possess do contain variant readings. And the most significant differences among the various English translations are not based on choice of English words or style, but rather on which set of Greek manuscript copies the editors chose to work from when translating.