The book utilises a series of Scheme based teaching languages to teach about how to write functions for increasingly complicated data types. The language levels produce meaningful error messages for programmers of that particular level and goes on adding language features as you progress through the book.

The book furthermore teaches a design recipe which comes in handy when you are stuck with a problem. Basically it teaches you to write examples first so that you understand the problem instead of jumping onto the editor to write code first. The examples help you structure your data. The rest of the code follows from it.