The company announced Tuesday that the treats inside kids' meals would change until Feb. 15 as part of an experiment. The meals will contain one of five miniaturize-size paperback books.

The move encourages McDonald's partnership with literacy nonprofit group Reading Is Fundamental. The fast-food chain recently donated 100,000 books to the organization.

The Valentine's Day-themed books include "Clark the Shark Takes Heart," "Happy Valentine's Day, Mouse!," "Pete the Cat: Valentine's Day Is Cool" and "Paddington."

This is the third time McDonald's has temporarily swapped the toys for books. The Los Angeles Times reported that the company will distribute another 17 million children's books by the end of the promotion.