The margins of the game question the moment and the way ludic becomes something else. In the book-game these margins allow to probe the articulation between reading and play and their respective functions. The literary roots of readings-to-play allow to analyse the contribution of Fighting Fantasy Gamebooks to ludic dimension of the genre, where emerges alternative and the decision that slices it. The reading of these books elaborates trees of opportunities that draw up a possible typology of playful choices. The study of the constraints and opportunities they open, from the point of view of the text and its use, demonstrates the cross-fertilization of narrative and ludic approaches.