They have acquired more copies of it than of any other book. It is called a great work of literature, the first work of history. It is at the heart of Christianity and Judaism. Ministers, priests, and rabbis preach it. Scholars spend their lives studying and teaching it in universities and seminaries.
People read it, study it, admire it, disdain it, write about it, argue about it, and love it.
People have lived by it and died for it. Though Friedman neglects to add Islam to the list of religions inspired by the Bible, his observation is accurate. In spite of the obvious influence of the Bible, it does seem odd if not somewhat paradoxical that we remain ultimately uncertain as to who actually wrote it. Of course, scholars have their theories regarding its authorship, which they back up with appeals to textual and linguistic analyses, archeological findings, and historical conjecture. But ultimately, no one knows for sure who wrote what in the Hebrew scriptures.