Overkill is the fifth novel in The Zone series. The first five were published in Great Britain in 1980-'82, then reprinted in the U.S. by Zebra with "Men's Adventure" printed on the spine as the genre category. (Zebra continued the series with another four books, and apparently a tenth volume was released by an electronic-only publisher in 2007.) The books are set in Europe during a ground war between NATO forces and Russia in a wasteland that's been repeatedly blasted by atomic, biological, and chemical weapons. In this one, Major Revell's and Sergeant Hyde's company are charged with aiding in the defense of Hamburg, but they're too late. There's much savage violent warfare and war crimes and sex. Andrea, the beautiful psycho killer, has a rival named Inga; all of the rest of the females are prostitutes or victims. (Hence the mid-'80s men's adventure label.) Despite the future-setting, there's not much of science fiction feel to the book, because the war technology isn't much different from WWII. It's a competently done adventure and reads more like a shoot-'em-up video game narrative than anything else. It's not good literature but it is exactly what it wants to be.
For a guy who writes so much about erections, the author is incredibly homophobic in this work. The action scenes are alright, but the writing/editing is pretty sloppy and the continual focus on sexual exploits detracts heavily from the Cold War-turned-hot fury of the first book in the fury. We get very little character development as we did in previous books either.
The focus on war crimes towards the end was interesting but very "Red Scare" with no critical self-analysis of war crimes as a problem on both sides of these conflicts.