Lots of religion fiction exists all over this planet. I have not seen any proof that God actually was involved. It may have been just a case of various writers claiming, quite wrongly, that it was God who was the author, and they only wrote down what God wanted them to write. If God didn't write anything, then it is quite true that, as you put it, "not one word or letter has been lost."
..... As I keep repeating, read also the (2005) book by Bart D. Ehrman: "Misquoting Jesus. The Story Behind Who Changed the Bible and Why."