This study focuses on three Armenian gospel books with sideways-oriented illustrations dating from between the 11th and 14th centuries that are part of the ARMENIA exhibition in the Metropolitan Museum of Art between September 21, 2018 and January 13, 2019, and briefly discussed in the printed catalog of that exhibition. With the aim to supplement that publication, it provides codicological descriptions and digital diagrams of the illustrated prefatory matter of the manuscripts in question. The three diagrams give visual overviews summarizing the layout and sequence of the sideways-oriented illustrations, and thus supply a critical tool for comprehending these books themselves as medieval works of art.