I'd give you a different answer at different times but I'd say this is the best sci-fi novel you haven't read
https://en.wikipedia.org/wiki/Worlds_(novel)
though I'd say
https://en.wikipedia.org/wiki/Operation_Chaos_(novel)
is the best fantasy novel you've never read.
The Initiate: Some Impressions of a Great Soul (1920)
by Cyril Scott
Wikipedia, but I haven't had time to read the whole thing yet, and I doubt most would consider it to be a book. It can be downloaded and kept offline, like a book.
I once read that if you tried to read every Wikipedia article for 12 hours a day, it would take you about 42 years to finish—assuming no new content gets added along the way.
The surprising health benefits of reading for pleasure.
https://time.com/article/2026/09/16/health-benefits-reading-...