1. Create book module by adding *Title *to corresponding field and save and display
2. You're taken to page to create first chapter. Add *Title *and *Content *to corresponding fields. Save changes
3. You'll be taken into the book and editing will be still turned on.
4. Hide the chapter you just created in the Table of Contents. All chapters are now hidden but you still have editing turned on.
5. Turn editing off in *Administration *block. You'll still be in book and still have the option to turn editing back on. Don't do so.
6. Navigate back to the course page and then click on the book or click on book name in bread crumbs trail to refresh page contents. If you just do a browser refresh, it is going to keep the session key and editing parameter in the URL but we need that cleared out.
7. Now back in the book, the table of contents will be gone and you'll get a message of "No content has been added to this book yet" and a Continue *button that takes you back to the course page. In addition, the *Turn editing on link is gone from the Administration block.
From an instructor's viewpoint, it looks like all their content is gone. To resolve, instructor must go back to the course page, turn editing on there and then go back into the book.
Video demo of bug - https://youtu.be/Orqo-LmnNyw
Tested and was able to replicate on my own site (2.8.10) and on core demo site (3.0.3 - as of April 11th, 2016). Assuming it affects everything in between as well.