2 Chronicles 27

Jotham follows his father Uzziah/Amaziah as King of Judah, when he is 25.  Jotham followed God's teachings, but did not go into the Temple as Uzziah had, and ended up with leprosy.  Jotham had likely been regent for some time before he actually became king.  This kings example and authority were not enough, apparently, to turn the people as a whole back to God.  The people continued to be corrupt. 

There is war with the Ammonites, and Judah prevails.  Ammon pays tribute to Jotham for three years.  Jotham prospers because he follows the ways of the Lord.  Jotham reigns 16 years, and then his son Ahaz reigns in his place.  So Jotham was 41 or so when he died.  This chapter gives us no information on cause of death.