I think it involved some sort of romantic subplot, but I'm not sure. I also remember it having the discussion of death, maybe of the main characters mother?
The most significant thing I remember is the main character talking about an experiment: A large amount of water was put in a vat, and it was watched to detect the disappearance of electrons/(protons/something like that). There was also a scene where the main character was sitting on a roof looking out over a town, and sees a flash that he thinks is one of the particles.
It was set in the United States in modern-ish time.
I read it within the last ten years.
It was a printed book, I think the cover was colorful but maybe not.
It was in English and not a translation (that I know of).
I read it in the U.S.A., I think I got it from a public library.