The Last Straw is the third book in Jeff Kinney's Diary of a Wimpy Kid series. It follows Greg Heffley as he continues to navigate the ups and downs of middle school life. In this installment, Greg's father, Frank Heffley, becomes concerned that Greg is not "tough enough" and attempts to toughen him up by pushing him into more athletic and outdoor activities. Frank’s ultimate goal is to send Greg to military school, which terrifies Greg.

Throughout the book, Greg tries to avoid this fate by attempting to change his behavior and improve his relationship with his father. As usual, his plans don't go smoothly, and he faces various challenges, including friendship issues, awkward crushes, and mishaps at school.