When I was a 15-year-old and was given the Book of Mormon for the first time, I was told by missionary couples that the Savior appeared to people who lived anciently on the American continent, and if I was to read this book, I could read about that account. I just was so excited to think that there was more scripture, that the Book of Mormon actually tells of a people that lived anciently and that the Savior appeared to them and He taught them, just as He taught in Jerusalem. If someone does have a belief in Jesus Christ but needs to know if the Book of Mormon's true, then, either way, to pray and to ask Heavenly Father if what they're reading is true. And they will feel it-- they'll feel it as they read it, that those words are true.