>> I hate to gripe but as of today I'm at Ruby/Rails book number 7  
>> and it
>> has the exact same info all over again on installing. Enough is  
>> enough.

No way. It only seems that way. because most books cater to people  
who are fairly new to Ruby or Rails.
Advanced books are always a tougher sell for publishers.
Ultimately, this type of content is likely a publisher/editorial  
decision in most cases.
Publishers already pressure most Ruby books' authors to include  
something about Rails.
The one thing that can probably be left out is the "getting up and  
running with Rails" sections. Particularly in books that don't go any  
further than that with the Rails topic.
But marketing is part of the publishing industry, and lots of  
publishers want you to buy their book and they know that a book that  
looks like it might have everything in it (broad, not deep) will  
usually sell better than a more narrowly focused book that goes  
deeply into one subject.

The same argument would make you say, " no more chapters about how to  
use [insert method or class here] "
Far better suggestion is what topics to write books and chapters about!

I suggest a GUI focused Ruby book that covers Qt, Tk, Wx, etc...
A game / graphics focused Ruby book... (could easily be integrated or  
connected with the GUI book)
A whole host of Ruby topics could be entire books based on one or two  
classes or modules or gems.
What we have enough of are books that are broad but not deep.
As an example: Pro ActiveRecord is a nice one, but an Expert  
ActiveRecord would be better...

Lots of topics to suggest.