I just noticed that a sibling comment has a link to Rainer Joswig's archive of the Dylan book (Dylan, an Object Oriented Dynamic Language, the book I referred to above).

Here's the link again for reference in context:

http://lispm.de/docs/prefix-dylan/book.annotated/

I should have known Rainer would have it.

Even better: he's also archived the design notes:

http://lispm.de/docs/prefix-dylan/design-notes/