For example, the text is a basic introduction to psychology intended for college freshmen. OR, the textbook is entirely theoretical, OR it takes a specific political position, etc., etc. Author describes the design of the text. For example, the chapters of the book are designed to be read in sequence. OR, the text is designed so that the chapters can be read in any order.
Author describes study aids contained in the text.
For example, many textbooks now contain chapter title pages listing the topics to be covered in the chapter. Many textbooks now have web sites designed to offer students supplementary learning activities. Author describes the source and design of possible exam questions. Many professors use the test bank as a source of exam questions. It is to the student's advantage to be aware of this possibility and prepare accordingly.