[JSWolf]

That CSS is very sloppy. It's not been cleaned. Also, the fonts used for embedding, remove them unless you need them. Minion Pro is a dreadful font on eInk. Don't make people suffer with it. I don't know the sans-serif font you've chosen, but dump that too and just use sans-serif as the font and let the default sans serif font be used. When you dump Minion Pro, also dump the entire font-family line. Do not leave in any font-family: serif.

If you are using that CSS as a house CSS, it needs to be cleaned up before being used and all the unused styles need to go for each book.