Researchers with a variety of academic and theological interests are proposing controversial theories about the Koran and Islamic history, and are striving to reinterpret Islam for the modern world. This is, as one scholar puts it, a "sensitive business" . IN 1972, during the restoration of the Great Mosque of Sana'a, in Yemen, laborers working in a loft between the structure's inner and outer roofs stumbled across a remarkable gravesite, although they did not realize it at the time. Their ignorance was excusable: mosques do not normally house graves, and this site contained no tombstones, no human remains, no funereal jewelry. It contained nothing more, in fact, than an unappealing mash of old parchment and paper documents -- damaged books and individual pages of Arabic text, fused together by centuries of rain and dampness, gnawed into over the years by rats and insects. Intent on completing the task at hand, the laborers gathered up the manuscripts, pressed them in...