ALGUNO V. NINGUN

Hola John C.

You're very close. In English, ningún usually corresponds to "no" or "not any", rather than "none".

So:

It can also be understood as You read no Italian books.

Saying "You didn't read none books" is not standard English because it creates a double negative.

As for algún/algunos, these generally mean "some" or "any", depending on the context.

For example:

So your intuition is on the right track, but it's more accurate to think of ningún as meaning "not any" (or simply "no") rather than "none".