Montana Harper, I believe you that
abnormal situations can produce unexpected results. A normal reader does
not read a new "book" every 5 to 15 minutes. Short stories are typically
collected in anthologies, instead of publishing every story, even one of only 500 words, as a separate "book". This just does not apply to 99.9999% of readers out there.
That said, I agree Marvin might handle such abnormal situations better. Let's see what Kris will come up with. As you say, if the EPUB code does not specify any font size, that font size should be sticky from book to book in Marvin. For me, it certainly appears to be sticky -- but I don't read a new "book" every 10 to 15 minutes.