Safely stored in archives’ storages across the world, ancient handwritten books (codices) that are too fragile to be opened, page-turned, or unfolded, are not open to consultation nor accessible, their content hidden from both experts and public. The main goal of the proposed project is to uncover their content and Reveal Unseen Text (RUTE) by reading through them without opening them. Current approaches for facilitating this task are mostly based on techniques that expose fragile manuscripts to ionizing radiation (e.g., X-ray computed tomography) potentially causing damage to ancient inks or support. To prevent damage of valuable manuscripts or written text, RUTE will exploit a non-ionizing technique, terahertz (THz) time-domain imaging, that can penetrate highly absorbing materials (e.g., paper, papyrus, or parchment) and detect paper-air gaps in the sample. Detected paper-air gaps lead to retrieving images that represent a single page of closed books often corrupted by severe system-induced blurring and noise effects. Until now, only limited attempts have been made to reduce these degradation effects (i.e., blur and noise) with none of them tailored to THz images that contain text. To fill this gap, RUTE will facilitate a unique approach to data creation and collection and introduce a highly interdisciplinary methodological process for reading through closed books. The proposed methodology will facilitate detection of paper-air gaps and pages separation, text enhancement, and document images restoration. RUTE will have a tremendous impact on analysis, preservation, and digitisation of valuable European and World cultural heritage assets by enabling the possibility to access knowledge that would otherwise remain undiscovered.