As with all of Shah's works one reading will not be enough. He did talk much of the conditioned mind, and I feel that Krishnamurti is a better speaker on the subject, yet I understand that there are forms of conditioning that are not apparent, and will reveal inner meaning to Sufi stories and ideas. The basic stages of development in Sufis and in other esoteric spiritual paths are similar, but it seems that not all of them share the same states, but perhaps similar stages. The Sufi will develop in a different way and with different perceptions than say a Buddhist practitioner.
He talks much of who is suitable for the path and who is not. He also speaks of the importance of not having a wanton grouping of students, but rather a group that is selected on the basis of aspiration, development, and potentiality. I think this is rather important, as only when these conditions are met, will we be able in my opinion to do real work for the benefit of others.
I would recommend this book to Sufis, but no one who is not engaging with Sufism. However Shah does point out the need for people uninterested in mysticism to have practice with Sufis, however how this could come to be I am unsure.