Actually it was written by 35 guys over a period of about 1,500 years. The amazing thing about that is that it is perhaps the most coherent book ever written.
Except that it wasn't written within 1500-year period.
There are no evidence that the Hebrew scriptures ever existing in the Bronze Age (c 3100 - c 1100 BCE). Although the Genesis to Deuteronomy - collectively known as the Torah to the Jews and Pentateuch to the Christians - there are no biblical writings existing in Late Bronze Age (c 1550 - c 1100 BCE).
Plus, the Hebrew alphabets were only seen in use until the 10th century (eg Gezer Calendar, the Zayit Stone; neither of them show signs having knowledge of the Torah or Pentateuh).
So if the Ten Commandment actually existed in the Late Bronze Age, the stone tablets would be written in Hebrew, so what writing were used?
Was they written in Egyptian hieroglyphs or Egyptian hieratic?
Canaanite cuneiform?
There are no literary evidence that the Bible existed in the 2nd millennium BCE. And no independent texts (eg Egyptian, Canaanite or Babylonian sources) showed signs that Abraham, Jacob, Joseph, Moses or Joshua living during the 2nd millennium BCE.
You only started seeing literary evidence that the biblical literature existing, is from 6th century BCE and later.
The oldest evidence was found in the Ketef Hinnom cave that served as a tomb, where silver amulet were found, badly damaged scroll containing the passage from Numbers 6. It is dated between the late 7th century and early 6th century BCE, so somewhere between Josiah's reign and before the Fall of Jerusalem in 587/586 BCE.
The Book of Daniel, on the other hand, was composed as late as first half of 2nd century BCE.
So I agreed with Subduction Zone, that the composition of Hebrew Scriptures were more likely 500-year period, not 1500-years which you have claimed to be.