To me this strikes me as a book that truly addresses the world of RSS and Atom. Their differences and how they are the same.

RSS and Atom in Action is organized into two parts. The first part introduces the blog technologies of newsfeed formats and publishing protocols—the building blocks. The second part shows how to put to those blocks together to assemble interesting and useful blog applications.

In keeping with the principle behind Manning’s “In Action” series, this book shows the reader, through numerous examples in Java and C#, how to parse Atom and RSS format newsfeeds, how to generate valid newsfeeds and serve them efficiently, and howto automate blogging via web services based on the new Atom protocol and the older MetaWeblog API. The book also shows how to develop a complete blog client library that readers can use in their own applications. The second half of the book is devoted to a dozen blog apps—small but immediately useful example applications such as a community aggregator, a file distribution newsfeed, a blog cross-poster, an email-to-blog gateway, Ant tasks for blogging software builds, and more. Source: Manning.com