This habilitation thesis undertakes a rigorous examination of the literary-theoretical dimensions of children's and young adult literature, with the objective of contributing to its theoretical and aesthetic discourse. At the core of this investigation lie two principal hypotheses. First, it is asserted that the persistent dialectic between heteronomous and autonomous aesthetic positions not only constitutes a foundational tension within children's and young adult literary studies but has also been instrumental in shaping both the historical trajectory and contemporary evolution of the genre. Second, the development of children's and young adult literature may be conceptualized as a continuous oscillation between the poles of aesthetic autonomy and heteronomy, reflecting broader shifts in literary, cultural, and ideological paradigms. Employing a comparative methodological framework, this study engages with an array of international children's and young adult literary texts published in the 21st century. The selection encompasses diverse textual forms and thematic orientations, including psychological fiction, cultural-ecological narratives, crime literature, and historical fiction. This corpus serves as the foundation for an in-depth exploration of the dynamic interplay between aesthetic imperatives and extraliterary determinants in contemporary children's and young adult literature, elucidating the ways in which these works navigate the dialectic between artistic self-determination and external sociocultural forces.