alt Hacker NewsI recommend these two books for 6502 assembly:
https://archive.org/details/ataribooks-machine-language-for-...
and
https://archive.org/details/ataribooks-the-second-book-of-ma...
These two books will give you a good understanding of 6502 assembler - it is general but gives a good background and has a nice assembler with a full walk through of the code. I used these two books to learn 6502 on my Commodore 64 and they are highly recommended.
These are great books. I had them in paper, and they were great for understanding both how the 6502 worked, and metaphors for managing higher level constructs in ML.