The four extant chapters of a vast astrological and astronomical encyclopedia, Sefer ha-Kolel (The Comprehensive book), are examined. Composed in 1256, and originally consisting of at least thirty-four sections (“gates”), it is conserved today only in Paris, Bibliothèque nationale de France, MS héb. 1058, fols. 50a–126a. It contains the oldest surviving copies of the astronomical and astrological works of Abraham Bar Ḥiyya (ca. 1065–ca. 1136) and Abraham Ibn Ezra (ca. 1089–ca. 1161). Unlike typical manuscript collections of astrological and astronomical texts, this work was compiled by an anonymous and learned scribe who made an intelligent selection of sources and interspersed them with his own articles and comments. This study has three main objectives: to identify, as far as possible, all the items in Sefer ha-Kolel, summarizing their contents and locating their sources; to study the encyclopedist’s role in the final shape of Sefer ha-Kolel by marking off his own comments and articles from the articles based on quotations from other authors; and on the basis of the study of the encyclopedia’s components, to place this encyclopedia in the context of similar medieval Hebrew texts, evaluate the encyclopedist’s modus operandi and distinct contribution, and produce a concise catalogue of the surviving part of Sefer ha-Kolel.