The book is published in 1997 or possibly older. I think it was part of a series. The book I read was an anthology with two or three stories in it. It appeared it could have been a collected edition of various pre published stories. Now the stories did not have a connecting characters it was the world that connected the stories.
Anyway one of the striking things about the book was it had different types of mutants. Animal/Human Hybrids created using genetics. They were all created by one doctor. The other two types of mutants were ordinary animal that grew to giant size and cancer ridden rabid beasts. There were floating radiation clouds when they engulf animals they became cancer ridden beasts. The giants were born that way. The book refered to these groups as mutants.
As for humans it seemed that a nuclear war had occurred but a little fuzzy on whether the US was still around.
Anyway thanks for any help.