The quality and accuracy of an open textbook can be addressed in a variety of ways. Here are some options:

By Author

Authors may invite and coordinate peers to review their work before publication. This review may be private or public — for example in the form of letters that are published with the text and included in the appendix. Reviewer names may also be listed in the front matter.

Faculty authors could ask, "If you were going to teach this in your classroom, what would you change?” This keeps the focus on pedagogy, since a textbook isn't scholarly research. It also means that the emphasis is on how best to achieve learning outcomes (rather than sales, for example).

By Publisher

Project managers who oversee textbook production may send the textbook, or portions of the textbook to reviewers. These reviewers may or may not have been identified by the textbook author. There may be modest funding to pay reviewers for their time. If so, stipends are often between $150-$250. Common turn-around times range from 2-6 weeks, depending on length and complexity. The process may be blind or open.

Publisher Example #1

For one example of a project manager's letter of inquiry to a potential peer reviewer, see this template from Deb Quentel, the Director of Curriculum Development and Associate Counsel at the Center for Computer-Assisted Legal Instruction.

Publisher Example #2

Dear [REVIEWER]:

Attached please find the manuscript for [TITLE]. Thank you for agreeing to review it. Our questions are as follows:

Is there something "new" here? What sets this work apart from others in the field?
What do you see as the strengths and weaknesses of the work?
Are the facts right? Has the author referenced relevant sources? Do the methodology and data seem to add up? Are any translations and quotations correct?
Is it well-written? Clearly organized?
Are there topics you feel should be covered that the author has not mentioned? Is there anything on which the author dwells too deeply? Do you have any additional suggestions?
Would the completed textbook be one you would recommend to students and colleagues?
May we share your identity with the author?

We would like to receive your response by [DATE]. In recognition of your efforts, we can offer you an honorarium of [AMOUNT]. In order to process this payment, we require the attached W-9.

Once you've completed your report, please email your comments and the completed financial paperwork. Once again, thank you for taking this on. We look forward to hearing your opinion on the manuscript.

Additional Questions for Reviewers

Do you teach a course for which this book would be appropriate? If yes, what is the title of the course? What is the level of the course (undergraduate, upper level undergraduate, graduate)? What is the approximate enrollment?
Is this book structured in a way that would fit your course? What big-picture structural changes would need to be made in order for the book to fit your course?
Is the book written at the right level for your students? Why or why not? What changes, if any, do you think need to be made?
How likely would you be to consider adopting this book if the author revises the manuscript in line with any suggestions you have made above (highly likely, somewhat likely, not likely)? What are the most important changes the author needs to make, if any, to make you more likely to consider adoption?
We see this primarily as a book for course use, but please tell us what potential you see for this book in other markets (among scholars, the general public, etc.)
Do you support publication of this book?

Additional questions from Supplement: Instructions for Reviewers, Content Module, Library Publishing Curriculum (CC BY).

By Student

Some faculty test their textbook in the classroom in order to incorporate student feedback. This method means that authors hear directly from their key audience about what’s working and what isn’t. For more information about beta testing open textbooks, watch this Office Hours.

By Library

Libraries sometimes collect and collate errata and feedback for faculty works they have published. This is typically gathered using a form on the institutional repository page where the textbook is made available for download. These notes can then inform future editions.

Textbooks in the Open Textbook Library may be peer reviewed using a rubric developed by BCcampus. The reviews are public and unedited, and appear with the textbook record.

Adapted from the Peer Review chapter in Authoring Open Textbooks (CC BY) by Open Textbook Network.

Additional Resources

Best Practices for Peer Review by Association of University Presses (AAUP)
Hypothesis
Rebus Guide for Publishing Open Textbooks (So Far) by Apurva Ashok and Zoe Wake Hyde
Textbook Reviews by Lauri Aesoph in Self-Publishing Guide