An experimental mutagenic virus from another planet is released over New York City and, over night, people are changed. Each change is unique and irreversible. Each victim is unique and the change itself has some relationship to the person they were before the virus took effect. Not everyone is affected, and many, the vast majority, find the change to be fatal. Of the survivors, for the vast majority, the change is either benign, veritably irrelevant or repulsive in some way.
But, for some, the change gives them "powers and abilities beyond those of mortal men." These latter are referred to as "Aces" and they have greatly enhanced powers, strength, psychokinetic, flight... whatever....
The books follow the adventures of, primarily, these "Aces."
It is truly a fascinating sci-fi premise and the books are well written, well edited and a delight to read.