The book Mathematical Opera or Mathematical Works on Geometry, Perspective, Architecture and Fortification by Samuel Marolois provides guidelines for drawing the four topics named in its title. The book is segmented into two volumes, which are both bound together into one single book. The first focusses on the topic of geometry and the second includes the remaining three topics on perspective, architecture and fortification. Each volume contains a text followed by illustrations and the beginning of each volume is marked by a full page illustration with the title. The texts contains theoretical explanations on the topics as well as descriptions and keys for the following illustrations. The illustrations are precise and technical, and the construction methods are clearly shown including construction lines. The book is therefore to be read as a guide. The first volume describes geometrical figures and their construction, with emphasis on the use of a compass. The second volume details how various perspective drawings can be constructed. The examples in the second volume focus on architectural structures and military fortifications. The book totals 675 pages, including 128 illustrations. At 220mm wide, 60mm tall and 310mm deep it is a large and heavy book. The dimensions render it closest to the Quarto standard book size, it does not, however, precisely match the specifications.