I'm trying to convert an azw book to epub. Calibre completes the conversion with no problem, but the font has changed (to something ugly). I know I can use the look and feel settings to fix this, but I'm curious why this is happening. When I look inside the resulting epub file, I find a number of .ttf files with names like 00001.ttf in the fonts folder, but when I try to open one, I get a message "invalid font file". The CSS refers to the font E B Garamond, which I don't have (though I do have Garamond).
I can use the look and feel settings to substitute the Garamond font, but why are invalid font files be written? Why does the CSS name a font not present in the file?