Everything you need to understand or teach King Javan's Year by Katherine Kurtz.
The great lords who plot against Javan have accumulated more power than the young king has and are less accountable for it. Accordingly, the theme of King Javan's Year seems to be "Absolute power corrupts absolutely."
Or even more dismally, it might be "Age and treachery will always triumph over youth and idealism."
The overall plan of the Gwynedd novels requires this type of ending. As one of Kurtz's admirers reminds us, two...