Image: opensourceway
Coursebook. Textbook.
They are terms that are very often used interchangeably, but I see what ought to be a fundamental difference.
Coursebooks have courses in them. That usually involves texts, but includes a whole range of other materials as well.
Textbooks (should) have texts in them. There can be different kinds of texts (and different ways of delivering texts) but I don't think they necessarily need to comprise or act like a (full, pre-planned and carefully sequenced) course.
I don't know... I just think it could be a helpful distinction to make and bear in mind when one is making and/or using course- and/or text-books.
;-D