The rationale of Interactive Digital Narrative (IDN) as media is to acknowledge the user at the center of the unfolding of a story, conveying vast yet sentient Interactive Narrative Experiences (INE). However, several challenges hinder IDN from reaching its potential, including the lack of appropriate methodologies for assessing engagement of narrative events automatically triggered in reaction to the choices of the user. But how to assess engagement of such a vast range of experiences? What are the characteristics of engaging INEs? This thesis tackles the previous questions by focusing on complementing existing approaches that consider the final ‘product' measured after the task. By keeping track during runtime of the dynamics of engagement operationalized as Continuation Desire, affect, and interactivity, this thesis proposes leads to enhance the measurement tools, fit strategies to model the fluctuation of engagement over time, and discusses the reconsideration of core dimensions of the INE.