Font size changes in one book changes all books…

I'm really enjoying the new iBooks service on my iPad. The only issue I have, more of an irritation than a major problem and I'm not sure if I'm doing it wrong or if it is an oversight with the way the iBooks app works, is that changing font size in one book changes the font size in others…

Currently I'm reading the Steve Jobs biography, mainly during the day, and also the Game of Thrones series, mostly at night before bed. The problem is, these two books have wildly different default font sizes - the Steve Jobs book having much larger text. If I downsize the text in Steve Jobs, it downsizes it in the other book too.

This wouldnt be such a problem except that resizing text reflows the whole book and I lose my page…

Is this an oversight with the app or am I missing some setting I should change? Or is this related to syncing between devices?

Any ideas?