This is an interesting premise. I liked that Nash and Myles initially entered their relationship and marriage in a very business-like manner, but we all know it can't be that simple, right? Myles is a paradigm of patience, intelligence, common sense and keeping cool. I didn't see him as a cold character, but someone who is very focused and only allows certain people to see his warmer, goofier side. I really liked him.
Nash, on the other hand, annoyed me a bit. He is obviously very jaded after the break up of his relationship two weeks before he was to be married, but I wanted to scream when kept mentioning that he was old (he's only 34), he didn't want to start from scratch relationship-wise and that he'd never find love again. I tried to be sympathetic to his situation because I knew he was really hurt, but after a while he just came off as a petulant and whiny. He didn't get what he wanted, so there was no hope for him.
The side characters were all very likeable and added a nice amount of depth and complexity to the main characters' lives. All in all, this is an enjoyable read.