***Not a teacher***
Hi Vil,How well has the author accomplished what he set out to do?
She has set out to get revenge.
In both these cases, 'set out' means 'began a process with a specific goal in mind'. I assume it derives from the idea of setting out on a journey to a particular destination.
So, the author began writing with the intention of imparting something specific to his readers - did he achieve this goal?
The woman concerned has very intentionally begun a process with the aim of getting revenge.