\paper vs. \layout again

[Graham Percival]

OK, I'm finally cleaning up our screwed-up docs on spacing and \book.  
I have a few questions, some of them fairly basic.  (further evidence 
of just how bad our docs are)

- In the 2.9.7 docs (currently online), in 10.4.2 Paper formatting  we 
have a list of \paper variables.  Can any of those be defined in a 
\layout{} block and changed for different scores?  In the example 
below, the "indent" has different effects, but the between-system-* 
vars don't seem to have any effect at all.

I'd like to document book-wide \paper commands (such as margins and 
print-all-headers)  and score-specific \layout commands (such as indent 
and... anything else?)

----
\version "2.9.8"
\book{
  \score{
    { \repeat unfold 100 c'4 }
    \layout{
      indent = 3.0\cm
      between-system-padding = #20
      between-system-space = 10.0\cm
    }
  }
  \score{
    { \repeat unfold 100 c'4 }
    \layout{
      indent = 7.0\cm
      between-system-padding = #1
      between-system-space = 0.5\cm
    }
  }
}