Verse 25. "Behold, they are written in the lamentations." - The Hebrews had poetical compositions for all great and important events, military songs, songs of triumph, epithalamia or marriage odes, funeral elegies, &c.
Several of these are preserved in different parts of the historical books of Scripture, and these were generally made by prophets or inspired men.
That composed on the tragical end of this good king by Jeremiah is now lost. The Targum says, "Jeremiah bewailed Josiah with a great lamentation; and all the chiefs and matrons sing these lamentations concerning Josiah to the present day, and it was a statute in Israel annually to bewail Josiah. Behold, these are written in the book of Lamentations, which Baruch wrote down from the mouth of Jeremiah."
Verse 27. "And his deeds, first and last" - "The former things which he did in his childhood, and the latter things which he did in his youth; and all the judgments which he pronounced from his eighth year, when he came to the kingdom, to his eighteenth, when he was grown up, and began to repair the sanctuary of the LORD; and all that he brought of his substance to the hand of judgment, purging both the house of Israel and Judah from all uncleanness; behold, they are written in the book of the Kings of the house of Israel, and of the house of Judah." -Targum. These general histories are lost; but in the books of Kings and Chronicles we have the leading facts.