Anathem by Neil Stephenson. An ontological speculative fiction set on planet Arbre, the book centers around Fras and Suurs (similar to monks) who, within their monasteries, instead of expanding upon religious endeavors, seek to expand on intellectual endeavors concerning physics, metaphysics, existence, and physical and social sciences. I allowed the book to fill my mind with the questions it wanted me to take from it, such as Many-worlds Interpretation of quantum physics (in short - all possible pasts and futures are real somewhere in the infinite universe) and more importantly the discussions of Platonic Realism (the concept of universal truths -- there are many chairs, be we all have a universal concept of a chair) and it's relation to ethical realism (universal good or right and universal bad or wrong) and the almost antithetical discussion of Mathematical formalism (the idea that all concepts in logic and math have no meaning unless they are given semantics). How he wrapped all of this into a fiction, I can only praise, but it had to be, or I would never have understood the concepts.