Unfortunately, on occasion authors encounter a rare bug in our Browser writing mode, where they see an "Error" message on the Write tab, and they are unable to continue working on their book.
If this happens to you for a brand new book you just created, we recommend you create a new book and start over.
First, to avoid any confusion in the future, you will want to rename the problem book here:
...making sure to replace YOUR_BOOK with your book's unique URL.
Then, you should "Close" the problem book here:
...again, making sure to replace YOUR_BOOK with your book's unique URL.
With the problem book renamed and closed, you can just start a new book here.
We're sorry for not having a better answer for you when this error occurs, but at least you should not encounter this issue again, after you create a new book!
If you have actually written a substantial amount in your book, please contact us with the details at firstname.lastname@example.org, and we will try to help get you back to writing again!