Over the last year, I have picked up a few books on Ruby on Rails but the information exits me as soon as it enters. Creating a Rails book in the Head First style is what I needed personally. This is a beginners book, but when a book is subtitled "A learner's Companion", one shouldn't expect anything advanced. For those who are looking for an advanced book, then they should check out The Rails Way by Obie Fernandez.
Ruby on Rails is an interesting and controversial framework, and is often difficult to get beginners help for. There are quite a few elitists who frown on designers and newbies like us trying to learn a framework, so we can make our designs more interactive. But you know what...Tough. There are countless cases where an engineer falls short at the CSS/DOM level and the designer has to take over. This leads to designers having to learn a bit of engineering....
The best thing to do is start at the beginning and practice a lot. Head First Rails covers a lot of projects (interesting) instead of just one (an easy way to lose interest).
In a nutshell, Head First books are designed for a certain type of person. Some don't understand, and complain about them..."theres a lot of pictures", etc... but they miss the point of the books. They're for beginners who want to learn fast and want to retain. They're designed as an educational experience and not a reference. For reference, there's plenty of books by O'reilly and Addison Wesely and others to cover that.
One reviewer here claims that this book teaches old conventions, i.e. the doesn't teach the RESTful method. This is not true. There is an entire chapter devoted to REST, and the project is mashing up a Google map. REST is a trendy term, and can be learned in an hour. As a matter of fact, it took about an hour to do the Google/Ajax map mashup in Head First Rails... sure beats the typical digg/fake bookstore projects in the other Rails books.
Head First Rails has been a joy to read. Its one of those rare books that I carry around with me. If you want to learn rails not just in the modern style but also historically (and thats a big deal, there's tons of Rails 1.x sites out there that need updating), this is the one to start with. After this book, i recommend learning Ruby itself, either in "Learn to Program" by Chris Pine (for beginners) or "Programming Ruby" by Dave Thomas and Andy Hunt. After that, I reccomend "The Rails Way" as a reference by Obie Fernandez if you plan on staying in Rails. The Rails Way has everything one needs to know, but is definitely not for beginners. Start here.