[Adoby]

Calibre often truncate parts of the path in the calibre library. And adds a numerical ID to the path.

But typically you should not directly use the books that are stored in the calibre library. Instead you should use the save to disk or the send to device feature.

There are several reasons for this:

* The book files inside the calibre library may not have been updated with the latest metadata and cover.
* If you accidentally modify, rename or move a file inside the calibre library, calibre may loose track of it.
* You don't have control over the path and the filename.

When you use the save to disk feature calibre will update the book(s) with the latest metadata and you can also modify the path and the filename used when saving the ebook.

Some operating systems have limits on how long a filename and a path may be. That is a problem with the operating system, not calibre. Typically Windows. Try to save the books to a folder near the root to minimize the length of the path. Also there are functions in calibre that allows you to specify how the path or the filename should be truncated.

I use Linux and have never experienced any problems with long paths and filenames.

You can save yourself a lot of trouble if you regard the calibre library as a "black box" and don't even look inside it. Instead use only the calibre GUI to save books to disk or send to device, or even email.