Have you studied ancient Hebrew manuscripts?
There are textual differences between ancient versions dug up. The solidified Old Testament wasn't really established for hundreds, perhaps thousands of years. the Book of J for instance, is very different than other proto-Old Testaments, but the line of influence connected between the two show an oral tradition emerging onto the written page. There have been many versions, as oral texts are subject to change with cultural trends. What is preserved over time is what is relevant to time, and in those cases, as society shifted, so did the Bible.
Even the most religious of scholars, if they are real scholars, will not deny that the texts were assembled from earlier versions by editors, rather than handed directly in complete form from one source. That Moses, for all his worth, could write Hebrew, in the Biblical form, which by my reckoning wasn't even a written language at that point, is highly doubtful. Perhaps, if the story is true, and he was raised as Egyptian royalty, he would be able to assemble writings in hieroglyphics, but if you have ever studied or looked at the way hieroglyphics work, you would realize the written tradition in that case is not literary, and nothing like the Bible.
As for even the complete version, which we read today, as approved by the Chief Rabbis, or the Vatican, depending which religion you follow, that too is not completely understood.
There has been ongoing debate, especially amongst rabbinical scholars, into the meaning of words, to the point where certain words cannot accurately be translated. For instance, the fourth plague, usually translated as wild beasts, has no accurate translation, and various Rabbis have suggested that it was anything from Beatles to Lions. I think something as central to the core of the tradition, as that is a rather well known chapter of the book, that has unclear meanings proves that the text does not truly exist in an understood form, and naturally there are many versions, especially within translation, as the King James Version no doubt established the validity of English Royalty's religious dominance over the people.
the text isn't as simple as religious people suggest, Jesus didn't say any of the things he says in the Bible, as Jesus wouldn't have said anything in Greek, being a Jewish carpenter in a part of the world where not only was the bulk of the population illiterate, but also spoke Aramaic. Thereby, the text, even if true, cannot accurately reflect the truth behind it, even if it is historically based.
Perhaps this may interest you:
http://en.wikipedia.org/wiki/Higher_criticism