Neuromancer by William Gibson.
My brother (who was in college) turned me on to this when I was about 15 or 16. He also gave me the two follow up books Count Zero and Mona Lisa Overdrive.
This is (arguably) the birth place of the concept of a virtual reality internet. It’s difficult, but I even forgive him for coining my least favorite term in the world… Cyberspace.
He’s done many other books but they don’t really feel the same as these three. I like them, but they haven’t changed my world the way that these have. When people talk about “formative years” it makes me think about reading these.
For years I would pick the name Hideo when playing RPGs or online muds and video games. Someday I will have my own vat grown ninja.