bookcrossing consists of abandoning books in public spaces so that people can pick them up, read them and then abandon them again for the next anonymous reader. for mahou san miguel and the madrid city council, we organized this event in collaboration with the balthazar agency in madrid, with the triple purpose of promoting volunteering, promoting reading and raising funds for youth aid programs. this was the largest book release in history: in a single day, 600 volunteers abandoned more than 30,000 books in the streets of madrid. a microsite was created for readers to register each book they found and read. for each book registered, mahou san miguel made a donation of €3 to a social and labor insertion program for young people at risk of social exclusion in madrid, carried out by the city council.