As far as I know, the Naqshbandis guard in high esteem the Shams al Ma3arif of Ahmad al Buni. Is the other great Medieval grimoire which is Ghayat al Hakim (Picatrix) of al Majriti or pseudo-alMajriti also reguarded as valuable, according to the Naqshbandis?
From a superficial perspective – never appropriate when considering the “hiddenness” of the occult – it would appear that both of these works are similarly concerned with dubious affairs relating to astral and talismanic magic. However, the foremost academic specialist on such matters in the world of Islam, Toufic Fahd, has in fact established an essential distinction separating them: only the work of al-Buni constructs a “temple” exalting the glory and omnipotence of Allah, offering nothing less than a “Qur’anic alchemy,” the elixir of which is the happiness of man. Such a description, however, is not really surprising, since the comparison of alchemy with the Science of Letters – the essence of al-Buni’s great work – has already been explained by Shaykh `Abd al-Wahid Yahya in reference to the initiatory rank of the “Red Sulphur.”
It is not without significance that your question concerns the “guarding” of the Naqshbandis. The very name “Naqshband” contains a meaning that is undeniably talismanic: “naqsh” being a term used in the Persian language for a talisman and “band” referring to the binding of influences through that talisman. Of course, the title of the order more likely refers to the imprinting of the heart with the Divine Name, and spirituality is only concerned with influences of the most superior domain. It would be appropriate, then, for a Naqshbandi initiate to safeguard the highest influences at work in the Science of Letters. For his part, Shamsuddin al-Buni, may Allah sanctify his secret, maintains that neither the origin nor the goal of his science belongs to an inferior domain, without, obviously, denying its operative virtues.
Even so, such matters are not without very real dangers. The Science of Letters (`ilm al-huruf) is in reality the Science of the Saints (`ilm al-awliya’), but those concerned with inferior domains belong rather among the “magicians and athiests,” at least according to the Shaykh al-akbar and Kibrit al-ahmar, may Allah sanctify his secret.