From Java to Ruby, Rails for Java Developers, and Everyday Scripting with Ruby

Bruce Tate is a popular Java author (Better, Faster, Lighter Java, Bitter Java and Bitter EJB) and blogger, so it's significant when he shifts his focus from Java. In the earlier Beyond Java (which I haven't read), Tate looked at what lead to Java's dominance, and the limitations that were creating opportunities for other programming languages. In From Java to Ruby: Things Every Manager Should Know (Pragmatic Programmers) Tate focuses entirely on Ruby, which he sees as a strong (but not certain) contender for the 'next' programming language (though it's unlikely that anything will be as ubiquitous as Java has been). As the title indicates, the book is targeted at managers. If you're a manager or team leader who needs an overview, perhaps because your developers are advocating Java, or you're a programmer who needs to think about about how to advocate for Ruby without your organisation this is a good book. If you're a programmer looking for details on programming in Ruby, you're better off with one of the books I talk about next.

If you're already familiar with web application development in Java Rails for Java Developers by Stuart Halloway and Justin Gehtland is an excellent introduction to Rails. It runs through a point by point comparison of web application development in Java (using Spring, Hibernate and JSPs) and in Ruby on Rails. It's a short, accessible book (292 pages), but it's not a replacement for Agile Web Development with Rails (Pragmatic Programmers) - if you're doing serious Rails development you'll still want that on your shelf as well. But developers who only need a comparison and an introduction, perhaps before they decide whether to jump into the deeper water, will definitely appreciate "Rails for Java Developers".

Finally, I'm reading (but haven't quite finished, because it's sitting on my desk at work as a reference)
Everyday Scripting with Ruby: For Teams, Testers, and You by Brian Marick. Although ostensibly targeted at non-programmers who need to 'get something done' with Ruby, I'm finding this to be an excellent Ruby introduction for anyone. It has the clearest explanation of regular expressions that I've come across - I'm weak on regular expressions, but after reading this book I was confident enough to apply them both willingly and successfully on my current project. Once again, this book isn't as deep as the Pickaxe book (Programming Ruby: The Pragmatic Programmers' Guide, Second Edition), but I think it's much more accessible. Definitely recommended.