wrong choice of words. I mean for tipical books.
ISBN is always better choice (more importance in the CV) as My specific situation is educational books, i have to write many many books, if I have to buy an ISBN for each book, I need too much money.
Besides, I do actualice often (for now). Sure in a point the book have no more changes. In that moment I can have the ISBN and mean time the ISSN (Educational use where the content have updates all the courses or classes).
I believe it could fix better and easy creating the metadata for Education LOM