Bibliobattle, a social book presentation game where battlers introduce their favorite book and decide the Champion Book by votes, has been spreading around Japan since it was invented in 2007. Although researchers and instructors have used its simplified variation, Mini-Bibliobattle, for second-language learners inside or outside a classroom, it is still unclear what books were chosen among winners and how they prepared for the presentation. Thus, this study investigated the champion books and their presenters through a questionnaire and interviews. It was found that the winners selected books with strong messages and clear storylines. Also, they elaborated their presentation by editing the composition and incorporating engaging tips such as asking questions. Tips for instructing Mini-Bibliobattle will be suggested at the conference.