The people of Israel are apostate, rebellious, and corrupt; only a few remain faithful—The people’s sacrifices and feasts are rejected—They are called upon to repent and work righteousness—Zion will be redeemed in the day of restoration.

• Isaiah

Either he started writing all of this after the reigns of the kings, Isaiah didn't write it, or he prefixed it later. See also Isaiah 2:1, which appears in the Book of Mormon. In Isaiah 6:1 and Isaiah 8:1 he speaks of himself in the first person.

He gives his testimony, after the prophecy, that it is of the Lord.

• Isaiah 2