Make sure you put your Text Book Zero language in your syllabus and in the message portion of this syllabus archive. (If you need assistance with TBZ contact Brian Newberry firstname.lastname@example.org).
For example, wording like this should be in your syllabus and here in the message here you post your syllabus.
Text Book Zero - The textbook is available in a digital format and may be purchased in the bookstore.
Also, please indicate if your course uses OER or other free text materials. Use one of these two statements:
This course uses some OER materials in addition to materials that require purchase.
This course has no text book costs.