As for the rest of the acts of Jotham, along with all his wars and his ways, they are indeed written in the Book of the Kings of Israel and Judah.
There is not much more related here concerning Jotham than we had before, Kg2 15:32, etc. I. He reigned well. He did that which was right in the sight of the Lord; the course of his reign was good, and pleasing to God, whose favour he made his end, and his word his rule, and (which shows that he acted from a good principle) he...
Commenting on 2 Chronicles 27:1-9
He was twenty five years old,.... The same is repeated here as in Ch2 27:1. 2 Chronicles 27:9
The rest of the acts of Jotham, and all his wars, and his ways - It was in his days, according to Kg2 15:37, that Rezin king of Syria, and Pekah king of Israel, began to cut Judah short. See the notes on Kg2 15:36, Kg2 15:37. Written in the book of the kings, etc.