Astrolabes, beautiful metal devices used for calculating time using the stars, and one of the great scientific inventions of medieval Islam, are documented in encyclopedic detail in this massive volume. King (history of science, J.W. Goethe U., Frankfurt, Germany) presents 20 essays, half of them previously published in other languages or earlier versions. Ten essays are devoted to specific astrolabes now in museums and originally made in medieval Spain, Yemen, Iraq, Iran, Syria, India, and the Ottoman world. (He uses the term "medieval" in the title to denote an Islamic era "neither classical nor modern.) The chapter on the 8th-century astrolabe in the Archaeological Museum in Baghdad includes a survey of all the astrolabes contained in that museum. A lengthy (110-page) initial chapter surveys astronomical instrumentation in the Islamic world. Other chapter topics include a lengthy treatment of the formula used for timekeeping, universal horary quadrants and dials, the origin of the astrolabe according to medieval sources, astronomical instruments used in Muslim India, geographical data on early Islamic astronomical instruments, and the quatrefoil as decoration on astrolabes. A checklist identifies all known Islamic astronomical instruments up to c.1500, grouped according to location. Each chapter is richly illustrated with b&w and some color plates. The first volume (published by Brill in 2004) presented an analysis of over 500 manuscripts documenting the use of the sun and stars to keep time, an essential task in Islamic lands for determining the hour of prayer.