I am not able to find where to change the font size on a Kindle book I purchased with my Surface. I was easily able to do it on my previous Samsung tablet which was Android based. Is there a way to change the font on the surface?
According to the description of the Kindle app in the Windows Store, it should be possible to change the font size.
I don't have the app installed on my Surface so I can't be sure but I suspect, like most native apps on Windows 8.1, you should open the Charms menu (by swiping from the right hand side of the screen or by pressing the Windows Key and C). You should then see Settingsor something similar. I would expect you to be able to change the font size in there.
If that fails, have you tried pinching the screen?