Donald Hamilton's series of books about secret agent Matt Helm stand as the overall best and most consistent series of books in the genre. Sure there are a few real clunkers in the series (The Retaliators is one I found very dull) but not many.
The Menacers is not the best book in the series but it's a great page-turner fun read. I highly enjoyed it, and in this he managed to keep me guessing.
I'd recommend to all who are new to the series to start with the first (Death Of A Citizen) as it's a well written book, not originally intended as a series book, and develops Helm as a character in a strong, realistic manner. It's the only one in the series where you really get to know Helm as a person rather than as a narrative voice (although an interesting one, as in better detective novels). Then I'd try THE SILENCERS or THE WRECKING CREW. This book, THE MENACERS, would certainly make an enjoyable third dive in to the world of Hamilton & Helm.