The Well-Grounded Rubyist is a forthcoming book by David Black, about the Ruby programming language, covering Ruby 1.9. The publisher is Manning.
It's likely to be a good Ruby book - here's why I think so.
David Black also earlier wrote the book Ruby for Rails which is popular and sold well. I own a copy of it - thought it was quite good. I recommend it (as one good Ruby book, not the only one), to anyone who asks me for suggestions for Ruby books, even for Ruby on Rails development, because:
a) there is a popular misconception that you can work well with Rails without knowing Ruby well - which is simply wrong - Rails IS Ruby - Rails is a web application development framework written in Ruby - so if you want to debug or just view the Rails source code (sometimes you need to do that to figure out what's wrong in your Rails app), you need to know Ruby quite well, and more important, to even do any programming in Rails, you basically have to program in Ruby;
b) Ruby for Rails is a good book explaining both general topics about Ruby, that are independent of Rails, as well as specific topics that show how to use Ruby for Rails development.
Of interest: the foreword to the Ruby on Rails book by David Heinemeier Hansson, creator of Ruby on Rails.
An interview of David Black on InfoQ.com
David Black's Ruby and Ruby on Rails consulting and training company, Ruby Power and Light
A review of the Ruby for Rails book on Vitamin, a popular web development portal.
Vasudev Ram - Dancing Bison Enterprises