Top down reference for Rails?

I appreciate the blend of demo development with top down perspective
-- big picture view -- of the Agile Rails book. Is there a reference
that focuses on the big picture view with less demo? None of the
Rails books I've checked on Amazon seem to offer this. Perhaps there
is an online reference I don't know about? TIA.

http://api.rubyonrails.com/

Quoting Ming <minger@gmail.com>:

hi, thanks for the link.

is there another reference that's less encyclopedic and more
explanatory on the architecture?

i found some on wiki.rubyonrails.org.

sorry for not posting a proper url, my browser is acting stupid.

Ming:

You might want to look at Ruby for Rails by David Black.