The Book of Mormon was written for our day.
15 Wherefore, I knowing that the Lord God was able to preserve our records, I cried unto him continually, for he had said unto me: Whatsoever thing ye shall ask in faith, believing that ye shall receive in the name of Christ, ye shall receive it.
16 And I had faith, and I did cry unto God that he would preserve the records; and he covenanted with me that he would bring them forth unto the Lamanites in his own due time.
President Ezra Taft Benson said:
“The Book of Mormon . . . was written for our day. The Nephites never had the book; neither did the Lamanites of ancient times. It was meant for us. . . . Each of the major writers of the Book of Mormon testified that he wrote for future generations. . . . If they saw our day and chose those things which would be of greatest worth to us, is not that how we should study the Book of Mormon? We should constantly ask ourselves, ‘Why did the Lord inspire Mormon (or Moroni or Alma) to include that in his record? What lesson can I learn from that to help me live in this day and age?'”
(“The Book of Mormon—Keystone of Our Religion,” Ensign, Nov. 1986, 6.)