For higher dimensional mind bending his Diaspora book is a must read!
For mind games: The Quantum Thief by Hannu Rajaniemi.
Plus for a related rabbit hole: the idea that a random pattern can just pop into existence and have consciousness is basically the https://en.wikipedia.org/wiki/Boltzmann_brain concept.
Diaspora was going to be my answer as well, the ending in particular. It kinda forced me to accept as inevitable that at some point my consciousness will cease, in one way or another.
I can plausibly see life extension technology arising that gives me hundreds, or even thousands of extra years of life. It doesn't seem entirely impossible to extend that premise to millions of years, but at billions it doesn't really seem fathomable, and trillions seems to be well beyond what we know about the likely fate of the universe. And once I accepted that inevitability, it suddenly seemed a lot more plausible that my time left was probably closer to decades than even centuries, let alone anything beyond that. There were definitely a fair few existential crises in the weeks and months after finishing that book.
Uuuuuhmmmm, yes, agreed. That whole story still gives me the existential shivers sometimes. The juxtaposition of the big and small. Brilliant, raw, too elegant, too calculatingly cold, too far out - and all because of its hardness (as in I don't even know if you have to suspend disbelief, it seems so perfectly real/possible), truly a masterpiece of science-fiction.
For mind games: The Quantum Thief by Hannu Rajaniemi.
Plus for a related rabbit hole: the idea that a random pattern can just pop into existence and have consciousness is basically the https://en.wikipedia.org/wiki/Boltzmann_brain concept.