Arabic authors frequently made use of past works, cutting them into pieces and reconstituting them to address their own outlooks and concerns. Digital technology can now detect, measure, and trace these repurposings, shedding entirely new light on how books were produced and received, how the Arabic textual tradition developed over time, and what its priorities and blind spots were. This technology, arising out of sequence alignment in genetics, the removal of duplicates in web-crawls and search engines, and anti-plagiarism software, is absolutely cutting-edge. One of the most innovative uses of it will be to map networks in new and more precise ways. In particular, historians are now able to discern much more easily transmission of texts across boundaries set by geography, sect, and genre. This paper focuses on text transmission across geography. It begins with a discussion of text reuse detection methods and specifically, how, building on our bibliographic data, our algorithms and visualisations can generate evidence for the transmission of texts. With reference to the presenters' web application, I highlight issues of methodology, and outline what our data can and cannot reveal. The heart of the paper focuses on the Arabic textual networks to which Khurasan belonged in the late 10th and early 11th centuries. In cultural history, this is an important region and period for the rise of Persian literature (e.g., Ferdowsi’s Shah-nameh, completed in 1010), as well as for the development of a vibrant court-centered literary culture in Arabic (as studied by Louise Marlow and Bilal Orfali, among others). I focus especially on the context of Abū Manṣūr al-Thaʿālibī (d. 1038), a man whose career benefited from the financial support of Sāmānid, Khwārizm-Shāh, and Ghaznavid rulers, and whose copious writings in Arabic provide extensive evidence for the world view of a major man of letters. I address three questions: first, based on our text reuse data, what can we say about the likely Arabic corpus of works available to al-Thaʿālibī? Secondly, by considering this corpus and citations from it by other, contemporary authors throughout the Arabic-writing world, what can we learn about the geographic spread and network connections of Arabic literature in al-Thaʿālibī’s lifetime? Finally, by examining the contents of specific passages, can we say anything particular about literary tastes in Khurasan, versus other regions? By addressing these questions, I will bring a new perspective to literary culture at this fascinating point in cultural history.