The dissertation relates to the importance and influence of usability in the processes of search and buying decision of books at online bookstores. The research is based on international known researchers' (such as Preece, Nielsen, Maurer, Haubl, etc) theories as well as usability testing results collected during the two-year research. The usability tests used resume in online questionaire, interviews with users, Think-aloud Protocol regarding e-commerce and search of obscure books of niche. Priority Matrix, Flow-task Observation and HeuristicEvaluation with usability specialists. Each result observed determined the sequential testing direction for purposes of comparisson between online and brick and mortar bookstores with marketing theories regarding purchase rituals, ambience and flaneurism. Personalized automatic recommendation and the possibility of digital handling of books' content in order to increase the possibility of buying decision are topics of discussion and testing that shows relevance regarding usability directions and user's expectations.