I arrived at the Victor party a bit late last year and was very impressed with the Hunter and the short story, Bad Luck in Berlin so of course I was going to read this next. Tom Wood as created a character you shouldn't really want to root for - a professional killer, friendless (mostly) and who we know very little about (unlike, say Barry Eisler's John Rain who has a very rich background), yet you find yourself compelled to see him through his situations, gradually learn more about him as he completes his contracts.
The Enemy can be read on its own without having read the Hunter (is situation with the CIA is explained) but I would urge you to read the other books. I noted recently to the author that he writes like someone who has written more books than he has released - there is an intelligence to the plots, the writing and characterisation and this book in particular is hard to put down.
The Amazon plot is a sufficient summing up of the story - I can only advise you to try this book and the author out (and the Hunter and Bad Luck too). If you're a fan of the international locales of Barry Eisler books and the tough man approach of Stephen Leather's Spider Shepherd character, then this book will be right up your alley :)