Part of the appeal of mysticism to me is how it offers a road. Avila suggests here that the Interior Castle of the soul is configured like a castle with many rooms that lead deeper and deeper to the center. So, the highest mystical plane is in the center, while the outermost room is the lowest.

This schema kinda gives you a path, a way to move forward in some way. I think in our contemporary "there's no purpose to life" worldview, things like this give structure and meaning, in that they promise higher truths and give you something like a path to get there.

Either way, it's an interesting book.

Also, I've read that Descartes probably got his notion of the deceiving demon in Meditations on First Philosophy from Avila, who was concerned that spiritual messages she received in prayer would be from demons pretending to be God. Pretty neat stuff!