Gods holy, sacred book, apparently dictated to faithful servants. As the WT says:
Most Bible writers acknowledged that they wrote in the name of Jehovah, the one true God, and that they were guided by him. Prophets who wrote the Hebrew Scriptures proclaimed more than 300 times: “This is what Jehovah has said.” (Amos 1:3; Micah 2:3; Nahum 1:12) Other writers received God’s message through angels.—Zechariah 1:7, 9.
The Bible was written by some 40 men over the course of 1,600 years. Some men were used to write more than one book of the Bible. In fact, the Bible is a miniature library of 66 books. It consists of the 39 books of the Hebrew Scriptures, called by many the Old Testament, and the 27 books of the Christian Greek Scriptures, often called the New Testament.
If it is so trustworthy, why does the WT feel the need to change anything?