This short book is for .NET C# developers who are curious about the Open Web Interface for .NET (OWIN) specification and Project Katana and want to learn more. The ecosystem of OWIN-based components is undoubtedly the future of the .NET framework-based web development. As a pointer of things to come, Visual Studio 2013 creates references to the Microsoft.Owin.* packages by default, for most of the ASP.NET project templates. The objective of this book is to introduce you to OWIN and Katana, the middleware goodness, and hopefully betters your understanding of OWIN applications.