I already knew a bit of Ruby and Rails when I started reading Rails for PHP Developers. After having read Pragmatic Agile Web Development with Rails, THE Rails book, this book presented nothing new to me. It may be a good resource for people that know PHP, but do not know Ruby and need to learn Rails in a urge. The comparisons between Ruby/Rails and PHP are the most valuable content of the book, and you can learn some interesting stuff from them.
If you don’t need to learn Rails fast, you are better serverd reading the http://pragprog.com/book/ruby3/programming-ruby-1-9">Pickaxe Book first and then reading http://pragprog.com/book/rails4/agile-web-development-with-rails">Pragmatic Agile Web Development with Rails.
Book on Amazon: http://www.amazon.com/gp/product/1934356042