Some Authors are under the mistaken idea that they need to choose the font and font size their ePUB ebook should have.

On the iPad (in iBooks), the choice has already been made for you as you can see in this video:

It’s more important to make sure your ePub book is formatted correctly so whatever font or font size your reader chooses, s/he will have a good reading experience.

graphic of Judith Tramayne's signature for her video on Why you don't need to specify font and font size in your ePUB ebooks

P.S. While your waiting for my ePUB eBook Course to come out, why not check out my Kindle eBook Course.