@Anak,
I'm afraid I don't have an answer to your question, but I thought I'd mention the following that I discovered when I first got the Glo.
You should take care where/when you use the
font-family: serif statement. On Kobos it will usually display its 'Document Default' font (Georgia) rather than the serif font you may have selected from the font menu. In your example, you'll probably get away with it because the Kobo automatically overrides body {font-family: xxx} with your selected font, but if you use
font-family: serif at a lower level than body (e.g. at the <p> level or in a class) you'll get Georgia and it won't be changeable from the Kobo font settings. I've found it safest to not use
font-family: at all rather than code it as
serif.
I have not found this to be the case on any of my previous non-Kobo readers. Of course, I haven't re-tested since my initial experiments so I suppose it could have changed in the last 6 months.
A comment on your original problem - ignoring font-family: sans-serif/monospace seems to be very common on Android epub reading apps as well. It's why I prefer Mantano over some of the other major names.