Thanks Peter.
The one I put most effort into was a Truetype font called Caxton Book, a proportional serif font from Bitstream. It's fully embeddable (though I wasn't embedding it in the epub, just loading it onto the device and selecting it from the font menu) and has all the accented glyphs standard in Western European languages. Most of its letters looked very little like they do on a computer screen, and generally looked quite blobby (a highly technical typographical term, you must realise!).
I don't remember precisely which other ones I tried, but there were three or four. I disliked all of them, so ended up removing them.
Ah well, never mind. I'll see if I can engage JSWolf on the subject, and see what observations he/she might have to make. In the meantime, for the epubs I reformat for my own use (an ever-increasing number, even of many commercial releases I buy!) I tend to embed appropriate fonts for the headings and just use Amasis for the body text. That keeps me going, at least.
Thanks for your help and comments, Peter.