The missing books you refer to in the KJV are most likely the apocryphal books which are generally not found in any Protestant translation (NASB, NAS, NIV, RSV, etc.). The Protestant church generally does not believe these books are inspired and therefore canonical, that is authoritative and deserving to be a part of the Bible as the Word of God. The books in question are considered apocryphal in most Protestant churches, but are accepted as canonical in the Roman Catholic Church, the Eastern Orthodox Church, and the Armenian and the Ethiopian Oriental Orthodox Churches.
There are 14 of these books found in the Septuagint and included in the Vulgate but considered uncanonical by Protestants because they are not part of the Hebrew Scriptures. The Roman Catholic canon accepts 11 of these books and includes them in the Douay Bible.
The following explanation from the Encarta® 98 Desk Encyclopedia © 1996-97 Microsoft Corporation may
