That was...not bad but not brilliant either which makes is incredibly hard to write anything at all about.
I've read a few books/crime-novels that were written from the POV of - let's say morally questionable characters but I think apart from Leena Lehtolainen's Time to Die in which the protagonist kills abusive husbands that's the only one I read that is actually from the POV of a killer. Just like in Time to Die he only takes out characters that are even worse than him. Those who orchestrated the killing, those who were willing to sacrifice lives for their own gain, in one case somebody who is "only" guilty of not doing anything - of not stopping two IRA-members from killing two British soldiers, of not stopping two armed men who also threatened to make sure that everybody would know that it was him who saved two Brits which hardly would have been a good situation to be in. Conveniently that guy turns out to be morally very questionable in other instances. Which is really a shame because that could have made for an interesting question: Would Gerry, the protagonist, kill somebody who really regrets what he did and has become a better person or not?
By turning that character into pretty much an all-round arsehole that is conveniently avoided. Almost like the author wanted to write about a serial killer but not one who is that bad. The same was probably also the reason for introducing Marie, a Strong Female Character(TM) who has gotten on the wrong side of the IRA (sorry...the unnamed party with close connections to the IRA and the party-leader McGuinty) and now needs Gerry's protection. (There is also a small child...obviously). A really cheap way to gain sympathy for the protagonist (and frankly she stayed terribly colourless throughout the book).
Nevertheless the book was overall rather gripping, especially the finale. I'm not even the type for 'lone guy storms the castle' (well in this case a small cottage somewhere in Northern Ireland)-type finales but I just was glued to the pages and ignored my growling stomach because it was that great. Additionally it had some some thought-provoking observations about the Northern Ireland-conflict so while I probably won't read it again I also can't say I regret reading it.