The Summer Game started as a reading challenge in Ann Arbor, Michigan, but it didn't work very well. Kids who didn't like reading would slog through the requisite number of books to get points, then be done for the summer. Kids who read long books resented getting the same number of points as those who read short ones.
So around 2011, the library decided to pivot. Via NPR:

"Instead of a reading game, we started a library-using game," librarian Eli Neiburger explained. "It includes reading, going to events, using our website, discovering all the things that the library has to offer. And it has been successful beyond our wildest dreams."

The Summer Game's design, he said, was inspired by corporate loyalty programs such as Coke Rewards. Users earn points by solving puzzles, learning about local history and exploring neighborhoods. Points can be redeemed in the library shop for T-shirts, umbrellas and other merchandise, such as a very popular stuffed plushie animal that's updated every year. (The 2025 animal is a small, bespectacled flamingo.)

"I was certainly not expecting how intensely popular it would be with adults," Neiburger added. Women in their 50s and 60s are overrepresented among Summer Game players, he noted, which reflects library user demographics. He wanted to use the Summer Game to raise awareness that the library can be used to borrow tools, art and music as well as books, and that it offers help with homework, finding jobs and provides a third space for lectures and crafting.

"Parks and Rec is not just baseball, baseball, baseball," he said. "Why should a library just be read, read, read?" The Summer Game reflects an ethos of meeting patrons where they are. And its code is open access, so any library can download it.

The program is not unique. the Anne Arundel County Public Library, in Maryland, had a participation rate of 10% of the population from the last census for its "Summer @ Your Library" program, including gameplay and event attendance, according to a library manager. Librarians in Dover, Ohio, created a Pokémon-style card-collecting program. Called "Reading Dragons and Friends," it is available for other libraries to use.

I am 1000% percent behind any program that gets people to use their libraries. Nice way to reward those who do.