So true. It was possible to literally know everything about the Commodore 64, down to every single byte.
And it was so great just flipping the power switch and instantly being in a programming environment. That blinking cursor was so irresistible, it just screamed of infinite possibilities, if you just knew what to type. Seems tragic in a way that that kind of built-in springboard doesn't exist in modern machines.
I still have my copies of Mapping the C64, and the hallowed C64 Programmer's Reference Guide (complete with full hardware schematic poster).