Thanks for that. Now I've looked at more files, half of them don't work
For example, I have Flatland, by Edwin Abbot (from here at Mobileread)
it insists on showing up as Abbot_Flatland with no Author, even though I've changed the metadata in Calibre. It does the same in Kindle for PC too, so it's not the device.
How do I set the metadata for the file so that the Kindle sees it? Do I need to use the command line tools?