Author Brad Ediger has been kicking around the Rails scene since the pre-1.0 days. Though not a Rails "luminary" necessarily, he certainly qualifies as an advanced user. He is CTO for a Real Estate tech company called Tasman Labs and runs a web design (and Rails consulting) firm called Madriska Media Group. He seems like a sharp cookie and a decent writer.
Advanced Rails covers quite a bit of territory, going for breadth rather than depth most of the time. Each chapter covers a classic, pivotal development concern... well, at least most of them do. The chapters are as follows:
1. Foundational Techniques
2. ActiveSupport and RailTies
3. Rails Plugins
7. REST, Resources, and Web Services
8. i18n and L10n
9. Incorporating and Extending Rails
10. Large Projects
By "Foundational Techniques", Ediger is referring to Ruby and Rails techniques, principals and patterns like Metaprogramming, Don't Repeat Yourself, and Functional Programming techniques. The chapter also goes into a fair amount detail about the Object/Class/Module relationship. A bunch of this may not be particularly new material for most Rails users who've been at it for at least a few months. However, it's still nice to have all this stuff in one forty page chapter... good to have handy to refer to. Also, there are some nice nuggets in there that could save you some head-scratching. For example, what's the difference between Kernel#lambda and Proc.new? The answer is that, if you *return* a value from the block passed to Proc.new, the calling method is exited as well, abandoning any code that you might have after it.
If the first chapter feels like it's leaning towards a reference work, the second chapter — which digs into all the goodies offered by ActiveSupport and RailTies — pretty much falls over right into reference-land, complete with a method-by-method listing of features added to standard library classes. This may seem even more like just putting api docs available online into print, but Eidger defintely adds a bit more explanation. And, I haven't really seen anyone give a rundown of just what the heck RailTies does. That's the library that provides the glue to pull together the more famous Rails libraries to make it all work together as rails: generators, initializers, etc. There is definitely some interesting and not necessarily readily available information here.
Chapter three covers Rails Plugins, and is quick and painless. It explains the common files and directory structure in a plugin and talks about how Rails loads them. It also talks about using Piston instead of svn:externals to manage plugins and show some example plugins.
The following three chapters cover more of the classic eternal problems faced in running high-traffic sites: databases, security, and performance. These really make the most sense in an "advanced" book; they are the "brass tacks" that everyone must get down too if they go beyond the "toy app" stage. Ediger talks about the strengths and weaknesses of the various popular database systems. He also goes into the benefits of using the filesystem to store data, which is largely because web servers can make use of fast system calls to dump files straight into the TCP socket. He also covers some advanced db features like composite keys, stored procedures and clustering.
The security chapter isn't all that long and a lot of the info it covers can be found in beginner Rails books... SQL injection, cross-site scripting etc. However, the book would be remiss to not include this material and it is presented in a concise and complete manner. This would be good to refer back to now and then to make sure you haven't slipped in your security awareness. Ediger also doesn't hesitate to make specific recommendations, like "whitelist rather than blacklist".
He also jumps right into recommendations while writing about performance optimization in the next chapter: "Algorithmic improvements always beat code tweaks", "As a general rule, maintainability beats performance", "Only optimize what matters", "Measure twice, cut once". He then goes on to cover specific tools and techniques for uncovering your bottlenecks, from a quick explanation of basic statistics to using httpperf, benchmark, and Rails Analyzer Tools, improving database calls (using indexes and "include" on finders), and the various caching solutions. There is plenty of good information in this chapter; also a good bit of reference next time you need to track down a logjam.
Chapter seven covers RESTful Rails, from the very basic theory as outlined by Roy Fielding to exactly how Rails has chosen to use these concepts, and is the longest chapter in the book. The amount of coverage REST gets seems questionable since Rails has been very heavily into the RESTful approach for over a year and embraced the philosophy so thoroughly that it's hard to imagine anyone using Rails today without being exposed to the concepts.
On the other hand, one can still wire up verb-oriented actions in routes.rb and might be able to get away with ignoring all the RESTful goodness. So maybe there are some out there that can benefit from this chapter. Plus, having such thorough, theory-to-practice coverage allows the chapter to stand on its own as a solid reference to the whys and hows of RESTful Rails. It also has one of the better sections on RESTful routing that I have seen (routes being one of the more mysterious and sometimes frustrating pieces of Rails).
Rails has gotten plenty of grief for its lack of official support for Internationalization and Localization, but in Chapter eight, Ediger lays out the options, such as gettext, Gibberish, and Globalize. He is most enthusiastic about this last library and it does appear to be quite powerful, including support for translating strings, translating model fields, localizing numbers and dates, and even recording what needs to be translated by saving them in the database. Creating multi-lingual websites is a hard problem in any web-development framework and most other frameworks have plenty of head start. However, Ruby and Rails certainly isn't without options and it will only get better.
The next to last chapter of Advanced Rails runs through a number of alternatives to the standard components of the Rails framework. On the database end, it covers DataMapper, Ambition, and Og, giving this last one the most attention. For alternatives to ERB templates, Ediger talks about Markaby, Liquid and Haml, all in a very brisk fashion. He also talks about using traditional Rails components — like ActiveRecord and ActionMailer — outside of Rails applications. The chapter closes with a discussion of how to contribute to Rails (hint: submit a patch... don't just bitch!).
The last chapter is called "Large Projects" and covers some useful information about working on a Rails project with a team, beginning with version control (though anyone who is writing code that covers more than a single file and *not* using version control is just plain insane). This starts with a quick overview of Subversion, however this feels like it is really a set up for making a case for "decentralized version control". Ediger does a good job of explaining these concepts, using Mercurial for his examples. This seems a bit unfortunate, since many people on the Rails core team have embraced Git and it is looking like Rails will eventually move its repository to Git. However, Mercurial has a reputation of being more user-friendly, so that may have influenced his decision. And it's useful information regardless.
Chapter ten continues on to discuss avoiding migration numbering collisions, issue tracking, keeping Rails and required gems within a project, web servers, load balancers, production architecture and deployment tools like Capistrano. This is all covered in a fairly quick fashion so don't expect a lot of depth.
That last sentiment came up often while reading this book. It often felt like Ediger was trying to get every possible Rails-related topic into the book that he could, but didn't want to come out with some 1000-page behemoth. Plenty of the topics mentioned don't have much more coverage than you could get with a quick "googling". However, there is something to be said for being exposed to a lot of tools, projects and concepts in one go, even if the exposure is sometimes superficial. I definitely found reading this book worthwhile and will keep it around to refer back to now and then. I don't know if I'd go so far as to label it required reading, but then again books on web frameworks rarely are.