A very interesting article here (from Biblical Archeology Review) explains some of the difficulties in interpreting the source texts of the Jewish Scriptures (Old Testament).
Many people don't understand that some differences in the various English translations go all the way back to trying to interpret whether a certain segment of text was in the original and accidentally not transferred into a new copy, or whether it was not in the original but deliberately added to a later copy (perhaps as a "helpful" explanation). It's as much art as science in trying to determine such things, but wonderful that we have such good sources of quite ancient material available.
The article doesn't mention that most of the text between the different Hebrew manuscripts agrees very well. (Of course, the Septuagint is a translation into another language, and that's a whole different matter!)
And it's encouraging also that these discrepancies don't seriously affect any major Christian doctrines, because most of them concern relatively minor issues.
[The article doesn't mention it, but seeing how much more we know since the Dead Sea Scrolls were discovered beginning in the late 1940s kind of weakens any "King James version only" argument.]