Someone can correct me if I'm wrong, but I believe the screen memory of the Commodore machines (ViC-20, Commodore 64) were the most straight-forward. As opposed to the more janky Apple II memory map.

You could do a lot worse than picking up a new Commodore 64 Ultimate [1]. They're a more or less faithful remake of the Commodore 64 but have an HDMI port, SD card instead of disk drive, etc. You could learn BASIC, should be able move to assembly as well—a quick search pulled up a YouTube course on 6502 assembly for the Commodore [2].

(I realize I am not contributing "books"—but others have done well in this regard. I did want to share what I think is a pragmatic way to learn 6502.)

[1] https://www.commodore.net

[2] https://youtube.com/playlist?list=PLU1o_YShTPgoA7_nZ0PutqaPD...