There is a vast difference between the authenticity of works supposedly inspired by God, and those that are said to be the actual words of God verbatim. Many different religious text claim to contain the words of God but only a few (eg the Quran) claim to be totally and completely Gods word without any alteration, addition, editing, deletion, or any other form of change. Also to validate that something is indeed divine and not simply the figment of human imagination and longing once must examine it's historical context, eg previous translations, and revisions throughout history, if these are identical or at least consistent, it goes a long way to allaying the fears that the "Word of God" myth is indeed a myth.

For all the scepticism, if any of these books do contain the actual word of God it is likely not to be immediately popular as it will ask for radical personal changes.