[benjiboy]

There are two questions there.

Part 1 - Because we can learn almost everything off the Internet, we are no longer held hostage to books.

Part 2 - Because the context Adams and others ZS gurus taught in no longer exists, except by choice.

Yes the basic principles still apply but the materials and tools have changed, the old books need an updating they don't seem to be getting.

There are plenty of modern books about The Zone System even as applied to digital photography just look on Amazon, and I find the idea of scholarship described as being "held hostage to books" ludicrous in the extreme.