Diary of a Wimpy Kid: Dog Days

The book opens with Greg Heffley and Rowley Jefferson going to his father’s country club after school closes for the summer, but Greg is kicked out due to his complaining of the smallest of predicaments. The beach trip that he was looking forward to is canceled due to lack of money, so the Heffleys resort to going to the town pool, which Greg hates because of its hairy and rotund visitors.

Later, Greg and Rowley have a sleepover together, and watch a horror movie obtained from Greg's older brother, Rodrick. After the movie, Greg and Rowley become scared of a muddy hand that might strangle them, which was in the movie. Unfortunately for Greg, his mother finds out about the movie after Greg's father told her when he found them sleeping in the bathroom, and starts a reading club in which he is the only participant after two days. The reading program, however, is put to a stop when Mr. Jefferson arrives with a huge $83 bill that Greg and Rowley spent on fruit smoothies at the country club, and he forces the boys to pay it off.

Greg’s birthday soon arrives, but the gifts he receives are all gifts he hates. Greg gets money in every card he receives, but Susan, his mother, confiscates it to pay off Mr. Jefferson. Uncle Joe’s dog, Killer, eats much of Greg’s cake, thus "ruining" his birthday. The following day, he and Rodrick both get fish as a makeup gift. However, when the family takes a trip to a water park, Rodrick's fish eats Greg's fish after Susan puts Rodrick's fish in the same bowl.

The next day is Father's Day, so the Heffleys visit Leisure Towers to spend the day with Greg's grandfather. There, Mr. Heffley tells of how his dog ran away to a butterfly farm. Greg's grandfather reveals that he had actually run the dog over and Greg's father takes off in disgust. He then buys a dog which Susan names "Sweetheart" and shortens to "Sweetie." Even though Greg has wanted a dog for a long time, he quickly becomes annoyed at Sweetie, who naps on his pillow, sleeps on his bed, and "won't stop barking".

The Jeffersons later invite Greg to go to the beach with them, which is where Greg had wanted to go, but he realizes it was far from what he expected, especially the Cranium Shaker, a ride that works like the "zipper" from RollerCoaster Tycoon 3. He tries to entertain himself, but he is sent home after he snaps a rubber band at Rowley.

Susan later tries to get Frank and Greg together, but both of them realize that they should keep their distance. However, they both hate much of the same things, such as a comic named Li’l Cutie.

The book ends with Greg realizing that summer is over when he sees a photo album titled "Best Summer Ever!" It is a "horrible record" of that summer to Greg, but Greg writes that the person who had taken the pictures told the story.