is word that is often used adverbially in Japanese to convey the meaning of ‘more and more’, ‘even more than (A)’, or ‘again’. This use is an extension of the base meaning that the kanji 更（さら） has in indicating that something is ‘approaching change’. Because of this, the expression used following 更（さら）に
will always be something that is either further along than the initial statement either in regard to time, quantity, or volume. Taking this into consideration, ‘in addition to (A)’ may also be used as a fairly standard translation.
is used adverbially, it often appears at the beginning of part (B) of a sentence, after the ‘base’ information has already been indicated.
The electricity bill has become even more expensive.
Sashimi tastes even better when served with soy sauce specially designed for sashimi.
When I installed antivirus software on my computer, my computer became even slower.
Fun-fact - The meaning of 更（さら） as ‘approaching change’ merely indicates that something has already reached ‘fullness’, and anything more than that will cause a fundamental change in the state of (A). Due to this, さらに primarily indicates things where (A) is considered ‘complete’ or ‘enough’ in and of itself, and what happens in (B) pushes that thing beyond a certain threshold. This may be either positive or negative depending on the sentence.
Ever since he started going to the hospital, he has gotten even better.
My life became even more difficult after being fired.