Verse 24 serves to move the text back to the Isaiah source. Verses 25 and 26 are essentially quoted from Isaiah 29:13 and 14.
Verse 25 speaks of those who pay lip service to the Lord. It was a theme Isaiah had introduced with the hungry man who only ate in dreams. There is the image of worship, but in truth humanity is far from the Lord. Isaiah says it of the children of Israel. Nephi expands it to his descendants and even to the gentiles.
The solution is that the Lord will do a marvelous work and a wonder. That marvelous work is what Nephi has just described as the coming forth of the Book of Mormon. Isaiah picks up on his theme that the wisdom of the learned is insufficient. That is recontextualized to mean that it is insufficient to just bring forth the marvelous work.