More than the story itself, that you can have summarized from the blurb, and that I would prefer not to develop more, I would like instead to talk about Arthur; the story has a lot of turn of events, and this contributes to the high pace said above. Enough to say that after all the high and down, Arthur's long and bumping life journey will end with him happy in bed with his lover, and I'm not spoiling anything, since the book starts like that, with Arthur satisfied in bed who goes down the memory lane.
Even if Arthur is a former marine, a former FBI agent and now a well-paid dogsbody who essentially has to protect Jeremy, he is not the hero type. All Arthur's grandeur gestures were made out of love or friendship, he has not a sacred fire inside for honor or patriotism. Arthur is a man who loves, and loved, too much, who can think to end his live when he is down, but that in the end never brings on the thought since he is able to love again. He loved Jeremy's father, Jonathan, and due to his betrayal he joined the Marine Corp; Arthur hoped to find in the Marine the family he hadn't and the comfort of being loved that he had with Jonathan. He did well and he opened his heart again, to Danny. But Danny died, that fathal September 11, and Arthur threw away his soldier life to commemorate Danny's love. And now Arthur is ready to love again, but at this point, it is real love, or only the memory of a lost love? or maybe the wish to finally have that family that he always searched and never found? In a case or the other, it's the proof that Arthur is able to love, and that despite all the time he was burned, he is always ready to love again.
Another thing I noticed in the story plot is that, despite being adventurous and fast paced, every events end in a "normal" way; there are not acts out of heroism, most of the time the decisive man is the one you will not expect, and even in the big action of the evil there is almost always a very small reason; and in the end, the novel closes with hope, and in a romantic way (remember Arthur in bed with his lover), but still in a very "pragmatic" way.
Amazon: Double Bound
1) Strings Attached: http://elisa-rolle.livejournal.com/1078527.html
2) Double Bound