I'm horribly embarrassed. Due to a software glitch, two of my ebooks have displayed wild changes in type size and fonts, often several sizes on a single page.
It's fixed now. If you downloaded Famous Potatoes or Clear Heart from Smashwords, you can re-download them now and get a non-glitch version. The words are the same, but the viewability is much better.
You should be able to re-download for free, if you've already downloaded them before. If you have problems, send me an email and I'll solve it.