As far as is known, Theophilus's was the only treatise on almost all the major arts that was produced during the thousand years of the Middle Ages. In his preface he presents the philosophical attitudes to the visual arts of a thinking man of the time. In his main text, which he divides into three Books, he explains the contemporary techniques of making wall-paintings, manuscripts paintings, stained glass windows, ivory carvings, and various kinds of metalwork. The first references to oil painting and paper occur in the treatise, which also gives the earliest known instructions for making an organ.

Theophilus's treatise has been of interest to scholars for some centuries. It was referred to by Cornelius Agrippa in the sixteenth century, and was the basis of an article by Lessing in the eighteenth. The original autograph manuscript has not survived, but the reconstruction of it by Professor Dodwell is now considered to provide its only definitive text: this comprehensive edition includes an English translation on facing pages and full introductory and textual commentary.