the plot alone of this book makes a great hook: a dystopian future brought about by contagious blindness. it's got all the hallmarks of a survival story without invoking zombies or a plague. when a character worries that fear of going blind might actually cause the blindness (and then goes blind), the reader becomes doubly afraid for themselves; it's no longer a book you are reading but an immediate and tangible Armageddon that could befall you in the next second.
this book reminded me of The Alchemist in that it has a loose story structure where many contemplations hang. there must be something about the Portuguese language that makes it compatible with philosophical thinking; perhaps there is an abundance of proverbs? There were many proverbs about sight or being blind, both explicit and implied, in the story. And even that was an exercise in philosophy because so many of our touchstones and sayings that take for granted sight become meaningless. and shared meaning is the basis of language so a lot of language disappears with the loss of sight, which leads to a type of loss in humanity, or at least what humanity used to be before the world losses it's sight.