Pressing the ENTER key while typing in a "Book and Quill" is intended to create a new line, which works fine on the first page of a book; But pressing the ENTER key on any page from Page 2 onward, will instead create and change to a new page, as the PGDN key would typically behave. The PGDN key still works as intended.

My ENTER key and ability to create new lines in other applications are both working as intended.