Recently just finished 'Killing the SS' by Bill O'Reilly and Martin Dugard. I get there are people who are not fans of O'Reilly due to his long affiliation with FOX News. If you can put that aside I think you'll find a well written and insightful book about the hunt for Nazi war criminals. As far as I could see the facts are presented in a simple non-partisan way.
Personally I was somewhat surprised to find that the US wasn't as keen on hunting these Nazi butchers as people might think. Reading how some of these barbarians eluded capture is frustrating and sobering but real nonetheless. The nabbing of Adolf Eichmann is an incredible story. I know a movie or two have been made about this but there really should be a big budget flick done... the true story is astounding.
It's also revolting to find out how accepting Argentina was of these war criminals.
O'Reilly has a whole line of 'Killing...' books. I will absolutely consider reading more of these titles. Easy to read and can be knocked out in a few days depending on your reading speed.