Having heard about this book several months before its publication, I was very happy to find that it had exceeded my expectations. As a Java developer very interested in Ruby, I was somewhat surprised at the lack of printed documentation on JRuby. I found this book to be very up-to-date, practical, and easy to follow, with examples that I could immediately apply. Particularly useful for me were the sections on setting up your environment with JRuby, Rails, and your preferred IDE, as well as deploying rails with various application servers. The instructions for all the main app servers on the market were extremely clear, and I was able to get things up and running in very short order. Also, I found the chapter on Enterprise Java integration to be especially useful, as it provided specific recipes for using JNDI, JMS, integration with Spring and Hibernate frameworks. I would highly recommend this book for any JRuby enthusiasts out there, looking for a solid and comprehensive springboard into the technology. Thank you Justin and Henry!
O'Reilly's Cookbook series is well known for providing short, pithy instructions for solving practical real-world issues in a well-organized recipe format. The JRuby Cookbook upholds that tradition, and I've found it a particularly invaluable source for help on JRuby-specific topics like integrating your JRuby code with legacy Java libraries or with services like JMS and JNDI. Clear, well-written JRuby-specific docs can be hard to come by on the web, so this book was a real life-saver for me. I frequently found myself wanting more though. The present edition is a great start, but those are big and complex topics, and more recipes, with more example code, would make it even better. So I'm appreciating the current edition, and at the same time hoping there will be a second, expanded one soon.
This book has a weird target audience. It's too advanced for people from beginning to intermediate, giving too little explanation to the recipes presented. The advanced user that would understand what's going on, would have no need for a book like this. The recipes are too basic to be of much use to a really advanced user and would be just as hard to figure out on your own as with this book. Additionally this book has a huge Java-developer bias, so a person approaching it from the Ruby side will be lost most of the time. I found the cursory explanations to the recipes fairly useless. Nothing more than the barest glimpse and then it's done. A thin volume, this book has no excuse for its lack of content.