- Age Range: 8 - 12 years
- Grade Level: 3 - 7
- Series: Diary of a Wimpy Kid (Book 4)
- Hardcover: 224 pages
- Publisher: Amulet Books; 1 edition (October 12, 2009)
- Language: English
- Product Dimensions: 5.5 x 0.9 x 8 inches
The book starts with Greg Heffley describing how he is an "indoor person," and how he intends to spend his summer vacation playing video games. His mother, Susan, wants him to go outdoors more often. Money is tight, so Greg and his family can't go to the beach. However, Susan still intends to have the "best summer ever."
Greg invites his friend Rowley for a sleepover, where they watch a horror movie about a muddy hand who strangles people, which scares them. They later start a lawn mowing service to earn money, but the job ends badly as neither of them have operated a lawn mower before.
During Greg's birthday party, Greg is gifted a Ladybug, a cell phone that can only make emergency calls and home calls. Greg is also disappointed that he didn't get a dog. Susan immediately took his birthday money to pay off Jefferson's bill. The next day, Susan takes Greg and his brother to the pet store. They are both given five dollars, so Greg settles on an angelfish. His brother buys a fish labeled "aggressive." After a trip to the water park, Greg finds that the aggressive fish ate his angelfish while they were gone.
At a Fathers' Day lunch, Greg's dad learns that his father accidentally ran over his dog when he was young, and then lied about him running away. He then drives off and buys a dog. Susan names him Sweetie, which nobody else is happy with. Greg does not like the dog, as he barks at the TV and licks his pillow.
In a picture, Greg notices Heather Hills, "the sister of Holly Hills, who is one of the cutest girls in my class" as a lifeguard at the town pool. He starts to help Heather out by getting her drinks and calling out people for breaking the rules. Greg runs away after Heather expects him to clean up a kid's vomit, deciding that he "need[s] to let this summer romance cool off a little."
Greg meets Rowley and his family at the supermarket. Rowley's mom asks if Greg would like to join them on their beach vacation, and Susan accepts for him. Greg struggles with the trip as he learns that their cabin has no electronics, feels sick after going on a boardwalk ride, and gets his dollar bill stolen. He "burns" Rowley with a rubber band, and is sent home early.
After this incident, Greg is afraid that his dad is going to sell him to an orphanage, and he calls the police with his Ladybug phone. It turns out that Greg's dad intended to take Greg to a baseball game, and he gives the tickets to the police. Susan is very disappointed since she brought the tickets for a father and son bonding. The next day, Greg's parents decide to give Sweetie to Greg's grandmother.
After hearing about a video game competition, Greg and Rowley decide to camp in front of its location. Greg gets chocolate on his hands, and decides to prank Rowley by making him think he is the muddy hand; this results in Rowley crushing Greg's hand with a mallet. Due to his injury, Greg is unable to play well in the competition and Rowley beats him and chooses a giant box of raisins instead of entering the competition.
The book concludes with Susan making a photo album and remembering the summer as the "best summer ever," although Greg thinks the opposite.
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