Just to clarify, I'm not arguing for font themes per se, just themes as they are now, except that today, Marvin understands "Themes" as the selection of text colour and background colour only
, whereas Stanza (and other e-reader apps, like i2Reader), interpret a Theme comprehensively
: comprising the entire look of the book, which besides text and background colours includes font types, font sizes, perhaps also other typographic features.
I admit that the second, more comprehensive interpretation of Themes strikes me as more logical. There's something "magical" (as Steve Jobs would say) about pushing the Night Mode button in Stanza, and instantly seeing the whole book transform before your eyes. In Marvin, switching to a different Theme simply swaps colours, so the effect isn't as eye-popping as in Stanza.
Now that you mention the wish list
, I'd also welcome the opportunity to store more than just 3 themes in Marvin because, as just discussed, themes suitable for reading Latin-based texts may not be ideal for reading Cyrillic-based texts, etc., so you quickly "run out" of the 3 slots currently available for themes in Marvin.