Despite the widespread popularity of online reading challenges on platforms like Goodreads and The StoryGraph, research on this phenomenon has been mostly absent. This article addresses this gap by examining the motivations of adolescent participants in reading challenges, the outcomes of their participation and the implications for their reading routines. Drawing upon semi-structured interviews with 20 participants aged 15-20 years, the article shows that motivations range from a desire for social engagement within a book-loving peer group to self-challenge. A common thread is that reading challenges serve as a catalyst for increased volitional reading by adolescents, accompanied by changes in their reading habits. Furthermore, analysis of the responses reveals that these evolving reading practices are perceived by participants as both stimulating and self-directed. However, the research also underscores the significant role played by algorithms on platforms like Goodreads in influencing reading routines. The study also shows that some participants in online reading challenges are guided by social motivation, although most of them experience social motives as secondary to their individual and intrinsic desire to read more. At the same time, some individuals partaking in online reading challenges prove susceptible to negative perceptions from others. Hence, this research foregrounds crucial tensions in online reading cultures adolescents engage in, specifically those between autonomy and algorithm and sociocentrism and egocentrism.