Chapter 11 is Nephi’s preface to his Isaiah section. He explains why Isaiah is so important and then he transcribes Isaiah 2-14 from the brass plates. Earlier, in 1 Nephi, he had included Isaiah 48-9 (see 1 Nephi 20-1). Jacob, had quoted Isaiah 50 (see 2 Nephi 7). Later, Nephi includes portions of Isaiah 29 (see 2 Nephi 27). Nephi’s great love for the words of Isaiah comes from the Spirit. Nephi had seen in vision many of the things that Isaiah was prophesying about (see 1 Nephi 11-14). Isaiah concentrated on some of Nephi’s favorite subjects, the house of Israel and the coming of the Messiah, Behold, my soul delighteth in proving unto my people the truth of the coming of Christ (v. 4).
Of the importance of the prophecies of Isaiah, the Bible Dictionary states:
"Isaiah is the most quoted of all the prophets, being more frequently quoted by Jesus, Paul, Peter, and John (in his Revelation) than any other O.T. prophet. Likewise the Book of Mormon and the Doctrine and Covenants quote from Isaiah more than from any other prophet. The Lord told the Nephites that ’great are the words of Isaiah,’ and that all things Isaiah spoke of the house of Israel and of the gentiles would be fulfilled (3 Nephi 23:1-3).
“….The reader today has no greater written commentary and guide to understanding Isaiah than the Book of Mormon and the Doctrine and Covenants. As one understands these works better he will understand Isaiah better, and as one understands Isaiah better, he more fully comprehends the mission of the Savior, and the meaning of the covenant that was placed upon Abraham and his seed by which all the families of the earth would be blessed.”
It is the opinion of the author of this website (BLR) that one of the reasons that the chapters of Isaiah were included in the Book of Mormon is because most of the latter-day saints don’t read the Old Testament. By including these chapters of Isaiah in the Book of Mormon, members of the Church who have a hard time getting through Genesis will still be familiar with the great prophet, Isaiah. If one includes Mosiah 14 (which contains Isaiah 53) and 3 Nephi 22 (which contains Isaiah 54), the Book of Mormon includes 17 of Isaiah’s 66 chapters. For the most part, the Book of Mormon includes the most important of these 66 chapters. Some of the other great Isaiah chapters deal with the Messiah and his Second Coming (see Isaiah 24, 42, 51, 52, 58-66). If we read only those portions of Isaiah that are included in the Book of Mormon, we will miss out on the great and profound prophecies contained in these other chapters. Truly, we need to follow the counsel of the Savior and study the words of Isaiah—even if it means reading the Old Testament. For as the Savior said, ye ought to search these things. Yea, a commandment I give unto you that ye search these things diligently; for great are the words of Isaiah (3 Nephi 23:1). It should be remembered that Isaiah is the only prophet whom the Lord singled out as a great prophet whose prophecies should be specifically studied.