There are also short term advantages to using the Calibre book id:
- In the new release I'm working on, if you choose to "add to existing covers" and inadvertantly copy the same book cover again you would just overwrite the earlier one rather than getting the same cover multiple times.
- It's easy enough for me to do (easily the most important consideration from my point-of-view )
The drawback may be the following scenario. You want to 'add to existing' the 10 covers from a whole book series. If you use the Calibre id the covers images will probably not be adjacent in the directory if you view them by filename. However, they should still all appear together if you view by date. Does this matter, I wonder?
Using author/title combination sounds appealing in theory, but filenaming conventions in non-English languages has got "can of worms" written all over it and I'd rather avoid it. Not to mention filename length, which would be difficult to read on a Sony if you were viewing images in "thumbnail mode".
I will ponder a little longer on the Calibre id option.
In addition, for those users who may have preferred to stick with the simple "single copy" option, I think I will retain the existing single filename of calibre_cover.jpg (or .bmp) so that no-one needs to reconfigure their device.