The Warrior Monk is part of a series of short stories accompanying the Seventeen series, and this particular story is best read after the second book: King's Crusade. In fact, I wouldn't start these short stories without having read the main series.
It focuses on the events that led to Alexa and Yonten meeting each other. While it provides some new insights into the background of the story, it was also a little bit repetitive with the story in the main series. It was also rather short (even for a short story), but nice to read nevertheless.