Not really.
Calibre can scale fonts, but that assumes they have the same starting point in each book. Some set the body High (>1 ) because the <P> was low (.755em appears frequently)
This is the reason I hand edit each book.
I use font-size: 1.2em for MY ,body class. (older eyes here), 1em might meet your BASE font needs This is always the same for ALL my books.
Basic P, (I assume (inherits) 1em start by using display:block

, I remove any font-size.
I scale other tags (h#, div, hr) and spans as needed
(boierplate styles get ~ .9em

)
By doing it this way, I KEEP dropcaps and other display font sizes
Without looking at the CSS (code) you don't know how the book was built.

Either way could result in the same appearence.