I know about the Book of Enoch, have yet to read it, but I know there are several other books that were not put in the final version.
I’ve also heard some grumbling about King James himself and his role so since there are many Bible wise Annons on this site, hoping you will share your knowledge.
One more thing. The Septaugint, being a Greek translation of the OT made by Jews, is useful for seeing what Jews really believed about the meaning of various OT scriptures, before Jesus was born. Jewish interpretation of OT messianic prophecies has changed since Christ, so it's good to see what they believed those verses meant with an unbiased eye.