I took some pictures of the three different font sizes that is available in iriver Story. The book I used was a EPUB book. I put the reader on a paper that have inches and centimeter ruler so you can get a reference size.
Default size (smallest):
http://www.ludd.ltu.se/~skyflyer/pic...StorySize1.jpg
Middle size:
http://www.ludd.ltu.se/~skyflyer/pic...StorySize2.jpg
Largest size:
http://www.ludd.ltu.se/~skyflyer/pic...StorySize3.jpg
In the new firmware that was released 2 days ago (v1.50) I also think that there is a function to add new .ttf fonts. But I haven't played with new fonts yet so I can not comment on it.