Neo Weird characters and fonts

[ivanm]

I've looked for this but haven't managed to find it: what kind of fonts (in terms of format) are we able to use and how do we specify using a custom font? This has recently started annoying me because I just bought Mission of Honor from Baen and there's all these question marks everywhere where I'm guessing the Neo couldn't show a particular character (Calibre's ebook viewer showed it properly however).

On that note, is there anywhere we can state that I always want to use a certain text size by default instead of increasing the font size every time I open a new ebook?