Developing your textbook structure
Building out the textbook’s structure is a good first step. This includes determining the tree structure and the structural elements. One way to accomplish this is with some sticky notes with structural elements written on them.
Process
First, start by asking yourself what you would like to call the “tree” elements of the textbook. Write each element on a sticky note. Be sure to include “Book” as the trunk of the tree structure.
Next, starting at the “Book” level, what structural elements will be included at the book level?
In this example, “Cover Page” and “TOC” are Openers at the book level, and “Index” and “Glossary” are Closers. The main content will be in the form of Chapters, which will be the next level of content that we will help structure.
Repeat this process at the “Chapter” level.
For each chapter, an “Introduction,” “Chapter Outline,” “Objectives,” and “Key Terms” are the Openers, and “Discussion Questions” and “Case Studies” are the Closers, with “Sections” as the main content.
Repeat this process for each tree level. When you’re finished, you will have defined what each level of the tree structure looks like, and will have taken a huge step in consistently structuring the textbook in ways that help the learner use the textbook effectively.
Keep in mind that this structure might change during the next step – defining the content structure – and this is perfectly acceptable.
Content structure
Note that the textbook structure defined above does not mention the course content. This next step involves asking the author to build an outline of content topics for the textbook.
Careful consideration should be given to the scope of the content in the textbook (what is covered and what is not covered) and the sequence in which the content is covered.
Scope
By scope, we are referring to the depth and breadth of the content to be taught. To be most useful, the scope should contain the content typically covered in a course or series of courses in a field of study. If possible, it could be very helpful for the author to get input from peers about the anticipated scope of the textbook before writing begins.
Sequence
The sequence of the content is the order in which the content should be taught for the best learning. In any given subject, there are likely multiple theories about which sequence is best (e.g., the OpenStax Chemistry textbook has been revised into a version called “Chemistry: Atoms First” because some instructors believe that it makes more sense to students to teach about atoms before teaching about other chemistry concepts).
The content outline
The author will need to create an outline that matches the number of levels in the tree structure. For instance, if the tree structure is 
then the outline will need to provide content for each level (below book). Here is an example of a portion of a content outline:
...
Unit 2. The Cell
Chapter 4. Cell Structure
Section 4.1 Studying Cells
Section 4.2 Prokaryotic Cells
Section 4.3 Eukaryotic Cells
Section 4.4 The Endomembrane System and Proteins
Section 4.5 The Cytoskeleton
Section 4.6 Connections between Cells and Cellular Activities
Chapter 5. Structure and Function of Plasma Membranes
Section 5.1 Components and Structure
Section 5.2 Passive Transport
Section 5.3 Active Transport
Section 5.4 Bulk Transport
...
Unit 3. Genetics
Chapter 11. Meiosis and Sexual Reproduction
Section 11.1 The Process of Meiosis
Section 11.2 Sexual Reproduction
Chapter 12. Mendel's Experiments and Heredity
Section 12.1 Mendel’s Experiments and the Laws of Probability
Section 12.2 Characteristics and Traits
Section 12.3 Laws of Inheritance
…
Source: “Biology” by OpenStax is licensed under CC BY 4.0.
It’s possible that the process of mapping out the content will make you realize that the textbook structure needs to be adjusted. This is perfectly normal, as the two structures are interrelated.
Note: When completing this outline, be aware that in 2012, open textbook publisher Boundless was sued by three publishers – partially because Boundless copied the structure of their textbooks. The actual content of the Boundless books was openly licensed, but the structure was mapped from the publishers’ commercial books. The case was settled out of court, so it is still unclear whether this violates copyright law, but you should be aware that it could be a legal risk to blatantly copy a commercial textbook’s structure.
Once complete, the Content Structure and Textbook Structure can be combined to create a complete outline of the textbooks. For example, consider a textbook with this tree structure:
Now, let’s look at two chapters of the content outline:
Chapter 11. Meiosis and Sexual Reproduction
Section 11.1 The Process of Meiosis
Section 11.2 Sexual Reproduction
Chapter 12. Mendel's Experiments and Heredity
Section 12.1 Mendel’s Experiments and the Laws of Probability
Section 12.2 Characteristics and Traits
Section 12.3 Laws of Inheritance
Combining these structures, we get the full outline of the two chapters:
Cover Page
Table of Contents
...
Chapter 11. Meiosis and Sexual Reproduction
Introduction
Objectives
Key Terms
Section 11.1 The Process of Meiosis
Main Content
Review Questions
Section 11.2 Sexual Reproduction
Main Content
Review Questions
Discussion Questions
Chapter 12. Mendel's Experiments and Heredity
Introduction
Objectives
Key Terms
Section 12.1 Mendel’s Experiments and the Laws of Probability
Main Content
Review Questions
Section 12.2 Characteristics and Traits
Main Content
Review Questions
Section 12.3 Laws of Inheritance
Main Content
Review Questions
...
Index
Glossary
Creating such an outline and filling in the outline structure with content will make it much more likely that you will end up with a textbook that is useful to students. It will contain consistent elements that will become familiar to students, giving them useful structure and scaffolding. The process of creating this outline encourages you to think through pedagogical tools that you might not have otherwise considered.
Attribution
