And let me add another one: "Coming to Ruby from Java", by Francis
Hwang

http://books.rubyveil.com/books/ComingToRubyFromJava/Introduction/ComingToRubyFromJava

Best regards,

Julian I. Kamil <julian.kamil / gmail.com>
http://pandora.rubyveil.com/ - Pandora Publisher
http://books.rubyveil.com/ - The Ruby Bookshelf