When you start illumination, you want to try different styles to see which fits your interest and talents best. This book creates a step by step walk-through for many different styles in a do-able manner for a beginner. But beyond that, the book provides examples of where to go from there. For instance, start of with the letter used as the example. When you finish that, try including one of the borders shown in that section using the same skills developed by following the example.
What this book accomplishes is to help you develop the "vocabulary" used by the sample styles. As you develop the vocabulary that the sample styles illustrate, you are on the path for more complex work (i.e. see Christopher De Hamel's books). Also, by learning the basics that this book provides, you are ready to play with styles not covered because you have the basis for where other styles came from or what they led into.