Mormon concludes by citing scripture, and seals this testimony with a final “and thus it is. Amen.”
Literary: This final phrasing is a formula seen frequently in the Book of Mormon to close sections, particularly sections with testimony. It consists of the two parts “and this it is,” and the “Amen.” Since amen may be understood to mean “so be it,” we have an interesting problem if we see the phrases as “and thus it is, so be it.” Rather that see it in translation as a phrase, it is probably best to see amen as a single word that serves as a final affirmation. In this function it could represent a word on the plates that had the same confirmatory function. The translation would then be something like “and this it is, truly.”
Textual: This is the end of a chapter. It is not the end of the book, however, in spite of the change in speaker that will come in the next chapters. From here Mormon turns to Samuel the Lamanite. That will serve as a new text and a new chapter. Mormon closes his text to this point with the end of the chapter. It is his specific homily that is closed with the formulaic “and thus it is. Amen.”