I've been a Java developer for about 10 years and I teach Java and XML software training classes for a living. Just over a year ago I was introduced to Ruby on Rails and found it fascinating. I dove in, excited at the potential ease and productivity gains, and started learning as fast as I could. My regular work, however, kept pulling me back to Java.
About a month ago, I attended a Java User's Group meeting in the Philadelphia area where Jason Rudolph gave a presentation on Grails. I found Jason to be a friendly, easy-going person to be around, obviously enthusiastic about Grails, and he gave a very enjoyable presentation. I learned that Grails can deliver most of the promises of Ruby and Rails (eventually it'll deliver on all of them), but with seamless Java integration, too. It's also built on top of Hibernate and Spring, both of which I've already invested considerable time learning, so I found that quite attractive.
Jason's book is like having him sitting by your side leading you through the framework step-by-step. He shows the design process and the natural development of a web-based, data-driven application, from conception to iterative delivery. The book is written as a series of short chapters, each of which adds a self-contained amount of functionality to the site. We get to implement it and watch it grow and improve in the process.
The books is short and very focused. In this age of massive, thousand page tomes that few people can find time to read, Getting Started with Grails is one of those few books that you'll buy and actually find the time to work through in detail. In all likelihood, you won't be able to help yourself. While reading it I was continually drawn to my computer, thinking, "it just can't be that easy, can it," only to find that it (almost) always is.
If I have any criticism of the book, it's that it remains true to its mission. It's like taking a tour through a new, interesting land with a great tour guide who obviously loves the place. I really enjoyed it, but it left me wanting more. Of course, that's the book's job. I will say, though, that while you may start with this book, it's very unlikely to be the only Grails book you buy.
The only other criticism I can think of is that Grails is still under such rapid development that the framework is a bit of a moving target. Any Grails book is going to face that challenge, of course. At least with this one, the basics seem likely to stay the same or reasonably similar, and the initial investment isn't really that high. It also helps knowing that Jason is one of the few committers to the project, so he really knows the details of the framework and where it's likely to be going in the future.
The author has done an excellent job showing newcomers what Grails can do and how to get started. I highly recommend it for anyone interested in what may turn out to be a very significant framework in the future. It's a great way to get started.