"Ascendance of a Bookworm" centers on Urano Motosu, a book-loving college student who tragically dies in an accident, only to be reincarnated as Myne, a frail five-year-old girl in a medieval-inspired world where books are rare and prohibitively expensive. Myne retains her memories and passion for books, but her new life in the lower-class district of Ehrenfest presents significant challenges. Her family struggles with poverty, and her weak constitution limits her physical abilities. Determined to read books again, Myne resolves to create her own, despite the lack of resources and technology in her new world.

The story unfolds as Myne leverages her knowledge from her past life to innovate and adapt. She begins by making simple tools like clay tablets and plant-based paper, gradually gaining the attention of those around her. Her ingenuity earns her the nickname "Bookworm" and leads to opportunities to interact with merchants, craftsmen, and eventually the nobility. Myne’s journey is marked by her relentless pursuit of knowledge and her efforts to improve her family’s circumstances. Along the way, she forms meaningful relationships, including a close bond with her adoptive sister, Tuuli, and her parents, who support her despite their initial confusion about her obsession with books.

As Myne’s reputation grows, she attracts the attention of powerful figures, including Benno, a shrewd merchant who becomes her business partner, and Lutz, a childhood friend who assists her in her endeavors. Her discoveries, such as the creation of paper and ink, begin to disrupt the societal norms of her world, where knowledge is tightly controlled by the nobility. Myne’s actions inadvertently draw her into the complex political and social structures of Ehrenfest, forcing her to navigate the dangers of a class-based society while striving to achieve her dream of establishing a library.

The narrative explores themes of perseverance, innovation, and the transformative power of knowledge. Myne’s journey is not without hardship, as she faces opposition from those who fear change and must contend with the limitations imposed by her frail body. Despite these challenges, her determination and resourcefulness drive the story forward, offering a compelling portrayal of one girl’s quest to bring books to a world that has long been deprived of them.