> there’s a distinction between the work (the book The Last Unicorn), the expression (a given edition of the book), a manifestation (a given physical format for an expression, such as paperback or hardcover), and an item (an individual object in a collection)

The author misunderstands 'work', as far as I know: A work is "intellectual or artistic content of a distinct creation. It refers to a very abstract idea of a creation e.g. Shakespeare's Romeo and Juliet and not a specific expression."[0]

In contrast, an "expression" is an "intellectual or artistic realization of a work. The realization may take the form of text, sound, image, object, movement, etc., or any combination of such forms."[0]

The Last Unicorn story is the work, "the book The Last Unicorn" is an expression as would be the film version or the computer game, etc.

[0] https://www.ifla.org/references/best-practice-for-national-b... (as of a few years ago)