Educators (with a Teacher account) have the ability to embed assessments in the margins of an ebook and share those assessments with the class.
The assessment creation tool is available in the web reader, but not in the mobile apps.
While inside your ebook, select some text to make the in-text toolbar pop up. Click Create Quiz.
The assessment creation window will open automatically.
You can choose to make a short-answer question or a multiple choice question. If you choose to make a multiple choice question, you'll need to enter answer choices and select the correct answer.
A question mark icon will show up in the margin for you and your students (if you click the Publish to Course checkbox).
When your students click on the icon, they'll have the opportunity to answer the question. When you click on the icon, you'll have the ability to edit or delete the question.
You can see a list of all the assessments in your ebook by clicking on the Overlays icon on the left side of your web reader screen.
You can see a similar list if you go to your course dashboard (My Courses -> click on your course icon) and click on Assessments on the left side of the page.
You'll see a list of all existing assessments, and you'll also be able to create a new assessment here. Note that an assessment created here will not be associated with any particular ebook or line of text (it will be a general, course-level assessment).