The Marin County Free Library’s summer reading program is underway, with challenges and prizes aimed at encouraging teens and kids to continue reading while school is on break. “It’s just one of those things librarians do to keep kids reading in the summer, to keep them from falling back,” said Kerry Livingston, librarian of the Stinson Beach and Bolinas libraries. “I’ve heard they can fall back a whole year.” Participants earn “book bucks” by reading or by completing activities such as visiting a park, exercising, telling a joke to a librarian or attending one of the many programs offered by the four West Marin libraries throughout the summer. This month, the Kenn Adams Adventure Theater brings its interactive drama production to the Dance Palace, and the Inverness and Bolinas libraries will host a slew of animals from the wildlife protection agency WildCare in August. Book bucks earn young readers raffle entries for prizes such as a telescope and tickets to a San Francisco Giants baseball game. They can also donate to Marin Foster Care or use their bucks to buy small items that range from jumbo crayons to a dinosaur fossil kit. So far, the summer’s most enticing reward has been a ballooning fad: “This year’s big thing are the fidget spinners,” Point Reyes Station librarian Dan Carr said. The summer reading program has become a tradition for Maya DeSantiago, who was the first person to sign up for the program in Point Reyes Station this year. The Tomales Elementary School student has been reading “The Diary of a Wimpy Kid” and “The Lion, the Witch and the Wardrobe” and has set her eyes on a fidget spinner.