Background: BookTok has become an influential short-form video community for book discovery and recommendation, yet the cognitive pathways through which eWOM information is evaluated, adopted, and translated into purchase intention remain insufficiently explained, particularly regarding whether product involvement conditions this process. Objective: This study examines the effects of information quality, information quantity, information credibility, and needs of information on information usefulness; the effects of information usefulness on information adoption and information adoption on purchase intention; the mediating role of information adoption between information usefulness and purchase intention; and the moderating role of book involvement in the information adoption–purchase intention relationship. Methods: A quantitative survey was conducted with 368 valid Indonesian TikTok users who had been exposed to BookTok content. Data were analyzed using PLS-SEM in SmartPLS with 10,000 bootstrap subsamples to evaluate the measurement model, structural relationships, mediation, and moderation. Results: Information quantity, information credibility, and needs of information positively predicted information usefulness, whereas information quality did not. Information usefulness positively predicted information adoption, and information adoption strongly predicted purchase intention. Information adoption significantly mediated the relationship between information usefulness and purchase intention (β=0.497, p=0.018), while book involvement did not significantly moderate the information adoption–purchase intention relationship (β=-0.014, p=0.417). Conclusion: BookTok eWOM influences purchase intention through a staged cognitive process in which perceived usefulness must be translated into information adoption before shaping purchase intention. The findings also suggest that high involvement with books does not necessarily strengthen the conversion of adopted BookTok information into purchase intention.