"The Passenger" and "Stella Maris" by Cormac McCarthy are fantastic. In general, I enjoy McCarthy's work because I believe he manages to present interesting ideas drawn from philosophy and religion, and if you read between the lines of his work, there is a fairly elaborate cosmology behind them. With these final works, he manages to combine this tendency with his decades of residence at the Santa Fe Institute and work with researchers in complexity science, mathematics, physics, etc. Moreover, he does so without the more trite ways non-scientists often draw upon science (for instance, just crudely using quantum mechanics as a stand-in for the supernatural). I think you could probably write a thesis on the way he integrated advances in complexity science and mathematics/physics with philosophy/religion/mythology with a close reading of his work. I mention this first and with particular emphasis because I believe it is chronically under-discussed and deserves a systematic study by someone who understands philosophy and modern physics and complexity science much better than I do. There is a hauntingly dark and beautiful cosmology behind this work, in a way even darker than his earlier works like "Blood Meridian."
I can also see the works of Arthur Schopenhauer being of great interest to many HN readers. His reconciliation of Western philosophy (especially Kant and British Empiricists) with Buddhism and Hinduism is unique and for me the most interesting overall system. His work is entirely worth reading for the quality of writing alone. For me, his works evoke the experience of mathematical beauty. I would recommend gaining a basic understanding of Kant, Buddhism, Hinduism, and then reading his work "Essays and Aphorisms," followed by "The World as Will and Idea."
"Propaganda: The Formation of Men's Attitudes" by Jacques Ellul is the book I have read that best explains the human experience in the modern media environment. Like "The World as Will and Representation," it also forms a sort of complete system, which can be read as an organic whole as well as with self-referential parts. I believe most of the "alienation" we experience from technology, which is often blamed on the internet, is really a much older and broader phenomenon, which Ellul attributes to the development of the radio, "technique," and broader phenomenological experience within 20th-century totalitarian societies.
"Simulacra and Simulation" is another that I have enjoyed. It is the work I have read that, in my opinion, best provides a model for living in a post-modern, post-industrial society, and my intuition is that it will also prove authentic in the age of artificial intelligence.