This book is project-based. The format of each project is similar, with a statement of the project, discussion of the main protocols involved, an overview of the API, and then complete code for building the project. You will be led methodically through concrete steps to build the mashup, with asides to explain the theory behind the code. This book is for Ruby on Rails developers who want to expand the features of their site by consuming remote external data and services. Basic knowledge of Ruby on Rails programming is required but you need not have any experience of any of the APIs used.