I definitely agree that Nasr's introduction is well worth reading. The subtitle, as Brian says, is philosophy in the land of prophecy, and Nasr goes out of his way to remedy rationalistic misunderstandings of Islamic philosophy and thought, emphasising the Islamic nature (its insistence on the oneness of God, its concern with being or Wujud) and creativity of Islamic philosophy. He also tries to correct the common Western misunderstanding that Islamic philosophy came to an end with Ibn Rushd (Averroes) or that Islamic thought is more or les synonymous with the voluntarism of Asharite Kalam. Often you would never even hear of the likes of Mulla Sadra in older Western histories of Islamic philosophy. Nasr is keen to show that, especially in Persia, the Islamic philosophical tradition continued until this day as a living tradition blending philosophy, gnosis, and faith, and that even some of its greatest practitioners lived long after Ibn Rushd. Even the Islamic Peripatetic school was revived by Al-Tusi and others in the thirteenth century. He also explores schools of Shi'ite thought and philosophy, such including the transcendent philosophy of Mulla Sadra and Ismaili thought.