However, a series of (chance?) encounters with Emily leads to friendship and his detachments begin to erode. For the first time (ever?) he begins to find a friendship and companion who he can share his thoughts and emotions with but at the same time feels safe because she's married. As I read this, I thought that he might actually have been using her marriage as an excuse NOT to get too close. Sure, she was married, and their relationship was "improper", but they did have a common bond.
It was when she touched his face to his that it all clicked for me. She got too close and he used his ability to emotional detach (hiding in a big city?) as an excuse to break off the relationship. The books he was reading suggest that he was conflicted about the relationship and was looking for a way to justify it. For example, when he wrote some quotes from Nietzche suggesting that men and women couldn't be friends because there was intercourse involved, he was using that as an excuse to justify his behavior.
Of course, after he found out that she was dead,it finally sank in. He was a cold hearted SOB and the one person whom he had an attachment to was now dead, possibly because of him. At this moment, he realized that he had blown it and that he may never find another. In her death, he was now unable to hide his emotions and detach. She had gotten to him in the same way he had gotten to her. He was heartbroken.