Ah, I see. Well, the broad strokes are definitely applicable and if you can find substitutes for the gems that I use (in particular, a background worker system, automatic state machine semantics for models, and a way to keep an audit trail) then the code examples will probably be at least understandable and sort of useful.
My guess is that an accomplished developer with a few languages under his/her belt might be able to understand and translate aspects of the code. At one point it becomes more opaque and you can't go further without learning Rails. I know nothing about Rails, which means I don't have a real sense of how difficult it might be for someone coming from, say, Python, to read and understand Rails.
Note: This isn't criticism. I am interested in the book but don't work with Rails and don't have the time to dive into learning it. Because of that I am trying to determine if the book would really be useful to me. I am currently working with Python and have good command of probably a dozen or more other languages.