Moving to egypt and converting to sufi Islam is not a rejection of gnosticism. Quite the opposite. It's not a rejection of Freemasonry or it's occusltism. Highly compatible. It's also a very modern, deracinated thing to do. He ran off to the ends to the earth seeking hidden knowledge. He got lost. That's the way that goes.
The truth is not an esoteric mystery. It's staring us right in the face. Reality isn't hiding in the shadows. It's the light itself.
I'm sure it's an interesting book and, like I said, his criticisms of modernity resonate. I'll put it on my list.