The book is third person limited told from the point of view of 13 year old Jonathan.
Jonathan, a thirteen year old boy, wants to fight in the Revolutionary War against the British. The book tells his story in the form of time-stamped episodes over a twenty-four hour period.
The difference between first person and third person is in the pronouns. A first person pronoun is I, my, me, we, and us. This would be evidence of a first person narrator. If Jonathan described his own life using I, then the story would be in the first person. Instead, we see third person pronouns like he and his being used.
Here is an example of the evidence of third person limited, shown through third person pronouns that only focus on Jonathan’s thoughts and feelings.
“What’s going on?” he asked.
“Soldiers,” said his friend, fitting the word between strokes of the bell.
A whip of excitement cut through Jonathan.
“Enemy ones?” he asked. (10:45, p. 12)
We know that the story is limited and not omniscient because we never get anyone else’s perspective but Jonathan’s. Even when we learn that his mother hates war, for example, it is because Jonathan is telling us. None of the other characters even have names.