What does it take to immerse oneself in a fiction? The main question of this dissertation is to consider the efforts, activities or tasks a player of live action role-playing games has to provide in order to immerse in a fictional universe. This game requires to adopt a specific commitment posture which main feature is that it works on a collaborative basis. In this PhD I use the following theoretical frames: Howard Becker on the concept of worlds and the division of creative work; Jean-Marie Schaeffer and the devices of fictional immersion; and Laurent Thévenot and Nicolas Auray on commitment regimes. I then consider three efforts, mainly using a strong ethnographic approach. The first is accessing the fictional world that implies the creation of an active and independent character; the second is interacting inside that world both by pushing and strengthening its frames; the third is about conceiving ways of organizing to provide frames of action.
