The Rosie Project

This was incredibly fun - mostly it's lighthearted and funny, but it carries a certain emotional freight toward the end. Nota bene: near the start of the story, there's a characterization of folks with Aspergers as being unemotional, which got under my skin quite a bit (challenged in reading social cues is emphatically NOT the same as lacking emotions). But if that bothers you, I urge you to read on. Remember, this is a first-person narrative, and a lot of the story is about Don's assumptions about the world and whether they turn out to be correct.

I also worried that this would become your standard Manic Pixie Dream Girl trop-ish story, but while Rosie qualifies for that role, the way Simsion makes use of the idea feels fresh and earned, not cliche.

Edited to add:

Reading a couple of negative reviews, I want to point out that the reviewers seem to have read the story at a shallow, face-value level.

Rather than taking a “point and laugh” approach, I felt like Simsion relied very strongly on sympathy with Don, twinned with a more savvy realization of where his perfectly understandable read on things is going to get him in trouble. For example, the argument about the superiority of his technical athletic jacket over a blazer. The reason it's funny to me is that Don's position is entirely justifiable and logical, and you kind of have to agree with him, but he's still totally wrong. (Or maybe the reader needs to have some rigid-ah, I mean organized tendencies herself to really get Don? It's possible.)

Moreover, Don is an unreliable narrator, and Simsion subtly and gradually brings out details that indicate Don's characterization of his experiences includes quite a lot of self-deception. There's plenty of “anguish and humanity” in him - it's just he has sophisticated defense mechanisms against realizing it.