Reading the Illegible examines the history of alphabetic writing in early colonial Peru, deconstructing the conventional notion of literacy as a weapon of the colonizer. This book develops the concept of legibility, which allows for an in-depth analysis of coexisting Andean and non-Native media. The book discusses the stories surrounding the creation of the Huarochirí Manuscript (c. 1598–1608), the only surviving book-length text written by Indigenous people in Quechua in the early colonial period. The manuscript has been deemed "untranslatable in all the usual senses," but scholar Laura Leon Llerena argues that it offers an important window into the meaning of legibility.

The concept of legibility allows us to reconsider this unique manuscript within the intertwined histories of literacy, knowledge, and colonialism. Reading the Illegible shows that the anonymous author(s) of the Huarochirí Manuscript, along with two contemporaneous Andean-authored texts by Joan de Santa Cruz Pachacuti and Felipe Guaman Poma de Ayala, rewrote the history of writing and the notion of Christianity by deploying the colonizers' technology of alphabetic writing.

Reading the Illegible weaves together the story of the peoples, places, objects, and media that surrounded the creation of the anonymous Huarochirí Manuscript to demonstrate how Andean people endowed the European technology of writing with a new social role in the context of a multimedia society.