I read pretty fast, but I must be your stereotypical millennial, because my attention span isn't very long, honestly. If I found a good book, that could be different.
This particular plotline is thus at the moment: the high schooler, Tristan, and the woman, Ingrid, meet at a physics lecture. She takes a liking to him and asks him to get coffee. There, she explains her (esp in combination) two physically debilitating illnesses and confronts his deeply-ingrained Catholicism. He's hooked, though, and goes to her art meetup the next Monday, where he meets her husband and learns she's a decade older. This is where it gets fuzzy for me, but I know not only does he have to reconcile his attraction, his (at least in the beginning) respect of her marriage, and the fact she challenges his piety, but her ailments seriously act up a few times, and the whole time which guy (Tris or her husband) she's leaning toward is pretty ambiguous.
In the end, she lets Tris down and the stress of the encounter incites a serious attack of her sickness. She has to go to the ER or even have some procedure (haven't decided). It works, but she gets hit by a car coming out of the hospital and dies. I'm going to explore the effects on the two guys a little, too.
I'm not sure how I'd learn; I've not done much "how-to" reading, but it's been helpful. I think with my limited (read: Twilight in high school) romance experience (I also haven't dated much). though, seeing "how it's done" might be better.