Ah, The Lamp of Non-dual Knowledge is quite the book, thanks for reminding me of it. Old school hardcore Advaita, 'shun the objects of the senses as if they are poison' style, and laying down a lot of the prerequisites for awakening.

I agree that understanding must be heartfelt and not merely intellectual, just as reading and learning words doesn't amount to knowledge. I like the analogy of food and digestion, as reading a recipe, preparing the meal, smelling the food... doesn't amount to eating, digesting and assimilating the food so that its essence becomes a part of you.

I've attached links to The Lamp of Non-dual Knowledge (Advaita Bodha Deepika) & All is One (Elam Ondre) another sweet little book recommended by Ramana.