Calligraphy and geometry, two of the most characteristic aspects of much Islamic art, receive full attention in this lucid analysis of the shifts in artistic practice of the 11th and 12th centuries that occurred throughout the Islamic world. Tabbaa, a specialist on the 12th-century leader and art patron Nur al-Din, has taught Islamic art and architectural history at MIT and the U. of Michigan. Annotation c. Book News, Inc., Portland, OR (booknews.com)