For those of you who want more of a choice which font to use. I haven't tested these fonts with the Cybook as I don't have one yet, but I know that they are of high quality and the Cybook's DPI should be high enough to render them nicely:
URW fonts (especially Garamond No8 and URW Palladio [Palatino clone])
Bitstream Vera family (also suited for low resolutions)