Vol. IV of the series Autographa Medii Aevi is a study of the original manuscript of the Liber Floridus (Ghent, University Library, MS 92). This encyclopedical compilation of the early twelfth century (finished 1121) was composed, written and illustrated by an obscur canon of the Chapter of our Lady in Saint-Omer (France, dept. du Pas de Calais). It may be considered one of the earliest illustrated medieval encyclopedias and its maps, diagrams and pictures (some of them masterpieces of Romanesque art) are world-famous. Due to its apparent lack of logical structure, however, Lambert's work has often been dismissed as an unorganized compilation. Against this still prevailing opinion the present book shows that the encyclopedia is the expression of a highly personal global view of the world. It was to be a brilliant synthesis, pervaded by an emphatic sense of symbolism, allegory and eschatology. The close codicological and textual analysis of the complete work shows also why Lambert failed to achieve his object in its full splendour; how especially external circumstances have caused a gradual weakening of the original train of thought as well as of the original beauty of the manuscript. The book focuses on the fundamental links between Lambert's thoughts and the material structures he had to create to give them their place in his book. Prof. Derolez has specialized for more than thirty years into the study of the Liber Floridus. In 1968 he edited the original manuscript in a celebrated facsimile and text edition. In 1978 his doctoral thesis on Lambert's work was published. The present work is the synthesis of a life's research. For the first time the complicated genesis of the Liber Floridus is unraveled in an international language. Languages: English, Latin.