In December 2008, the Merb team announced that they will be collaborating with the Rails core team on the next versions of Merb and Rails. Rather than maintaining parallel tracks, Merb 2 and Rails 3 will merge, preserving the flexible configuration and advanced features that Merb users love along with the rapid productivity and ease-of-use that makes Rails shine. As Engine Yard developer (and Manning author) Yehuda Katz puts it, "Effectively, Merb 2 is Rails 3." Rails 3 in Action will provide a thorough introduction to Ruby-based web development using Rails. Like Rails 3 itself, this book combines Merb and Rails in the form of authors Yehuda Katz, Merb Lead Developer. As a developer, you'll benefit from several big advantages to this change: Rails becomes more modular, by building on rails core with the ability to opt in or out of specific components and making it possible to replace parts of Rails without disturbing other parts. Merb performance improvements flow into Rails, including benchmarking applications so developers can see which optimizations have real-world impact. A defined public API with a test suite, so users and plugin developers have a stable API to build against. A "core" version of Rails, like Merb's current core generator, that makes it easy to select just the parts that are important for your app. DataMapper and Sequel support as first-class ORMs, along with ActiveRecord as the default. Rack support in Rails 3, to improve the state of modular, sharable logic between applications. The Rails 3 team is moving full steam ahead building the new version. The Merb team will start working on Rails immediately, and also continue to fix bugs and resolve other major issues in the current release of Merb. Interim versions of Merb will help ease the transition to Rails 3. In particular, Merb releases with deprecation notices and other transitional mechanisms will assist developers in tracking down the changes between Merb 1.x and Rails 3. If you've already learned Merb, Rails 3 in Action will help you parlay that knowledge into the new Rails code base. If you're a long time Rails developer, it will help you get up to speed with all the new Rails 3 features and changes.