[Tech Guy]

I started the content server from the preferences, and used the "test server" button to experiment within Firefox.

I found that when I click on the "Get" button in Firefox, I can see the name of the file that will be downloaded. They mostly have a leading underscore, mostly being an interesting word here.

What I finally found was that the files that are part of a series do not have the mangled filename, and they are prefixed by the series name followed by an underscore. The name used by the server is not the same as the filename in the library, nor is it the same as the metadata filename. This made it hard to figure out.

So, the filename as presented by the content server is: "series_Title - Author Name_nnnn.xxx", with nnnn being the number assigned by Calibre. Apparently, if there is no series, it is generating "_Title - Author Name_nnn.xxx", without detecting that the series name is blank.

I added a series ("X") to a book that had the leading forward slash on my Kindle, and the result was "X/Title - Author Name". So, that is the source of the forward slash.

I'm a bit surprised that only my installations do this, but I attribute this to bad luck and trouble, which is my middle name. Or names, I guess. :-(