Again Nephi references Isaiah 29 and his vision, see 1 Nephi 13:39. The Book of Mormon is obviously the vehicle by which those who are dead will speak out of the ground. The phrase, their voice shall be as one that hath a familiar spirit, could be interpreted to have a double meaning. First, in Isaiah's day, a person with a familiar spirit was someone who claimed to be able to speak with the dead. The voices of the ancient prophets, then, are heard in the pages of the Book of Mormon. Second, the Book of Mormon has a "familiar spirit" to all those filled with the Spirit of God. Through the light of Christ and the Holy Ghost, the righteous recognize the divine nature of the Book of Mormon. It is "familiar" in the sense that it carries the same spirit of truth and righteousness that the Bible does.