Since I'm not acquainted with 'the last straw christmas story', it's difficult to determine its main theme precisely. However, considering it's a Christmas story, it might revolve around the values that Christmas represents such as love, kindness, and forgiveness. The 'last straw' in the title might imply a tipping point in a character's journey during the Christmas period, which could be related to learning an important lesson, making a significant change, or experiencing a revelation that is central to the theme of the story.
Since I'm not familiar with this story, I can't give a proper summary. You could try providing more details about the story so that I can answer better.
Greg Heffley is the central character. His family members, especially his father, are important characters too. Also, his friends at school like Rowley are part of the main characters. Greg's experiences are mainly shaped by his interactions with these people.
The main plot revolves around Greg Heffley's family issues. His father wants him to toughen up, which leads to a series of comical and relatable situations. Greg tries to navigate school, friendships, and family expectations all at once.
The story of 'Last Christmas' often centers around people's relationships and how Christmas brings about changes and new perspectives. It could have elements like romance, friendship, and family bonds.
I'm not sure as there's not much information given just by this title. It could be the last part of a series of stories related to Christmas, perhaps about the final event, character, or moral lesson in a collection of Christmas - themed tales.