The book that was seen by Nephi being carried by the Gentiles in the promised land was, of course, the Bible. The meaning of the book explained by the angel is significant in light of the verses that follow. That it proceeded out of the mouth of a Jew, and is the record of the Jews seems to identify the role of Jesus in the Bible. As “the God of Israel, and the God of the whole earth” (3 Nephi 11:14), out of his mouth, a Jew, proceeded what was recorded in that book (v. 23). It was he who made the covenants with Adam, Enoch, Noah, Abraham, Isaac, Jacob, Joseph, and Moses; or with the house of Israel and those who preceded them. It was he who gave revelation to the patriarchs, prophets, and apostles, and inspired them to write the future happenings to the covenant people. It was his Spirit, voice, and will that spoke to Isaiah, Jeremiah, and all of the prophets until Malachi.
However, that book was not as large as the plates of brass which “did contain the five books of Moses, … a record of the Jews from the beginning, even down to the commencement of the reign of Zedekiah, king of Judah (the historical books); and also the prophecies of the holy prophets … and many prophecies which have been spoken by the mouth of Jeremiah.” And they also contained “a genealogy of (Lehi’s) fathers” (1 Nephi 5:11–14). Many of the writings that were in the Bible carried by the Pilgrims were written after Lehi left Jerusalem. These include part of Jeremiah (implied above), Ezekiel, Daniel, Zephaniah, Habakkuk, Haggai, Zechariah, Malachi, Ezra, Nehemiah and part of the historical books of Kings and Chronicles following Zedekiah (600 B.C.). A tabulation of the number of pages in the King James Version of these later written books shows at least a hundred and sixty pages of material, plus the four hundred pages of the New Testament that were not in the plates of brass, and yet the plates of brass were larger. Therefore, at least six hundred pages of materials have been lost from the present day Bible that Nephi is told about by the angel of the Lord.
Nevertheless, the covenants of the Lord to the house of Israel were retained, and these were of great worth to the gentiles.