[Adoby]

Calibre keeps track of what fields have been updated, even if you revert back to an empty field. If you press OK, then all the updated fields will be used to update the books. That is how calibre works. You may not like it, but you have to learn to live with it.

Sure there is room for some improvements of the GUI to make this more obvious. Perhaps a tick box for each of the fields that is automatically ticked when you update a filed, to indicate that calibre will apply the value of the field to the books. Also the Clear Series box may be a little confusing and redundant.

Feel free to refine and suggest this as an improvement of the GUI. Perhaps Kovid will fix it. But the dialog is already cluttered...

But I can live with calibre as it is now, I know how it works and it seems perfectly logical to me. And I prefer a simple GUI.