An uusual narrative development in Trust Exercise: Will it pay off?

The first half of Susan Choi's novel Trust Exercise includes and concludes with some really bad sex, by which I do not mean bad writing about sex (there's an annual prize for that!) but excellent writing about really bad sex. By the midway point I'm thinking: Why does the main character, Sarah, an intelligent and artistic young woman, put up w/ this horrible behavior and truly bizarre exhibitionism that she gets into w/ two men in her (young - she's 16 years old) in her life, one of whom seems to be considerable older than she? All men (and all sex) can't be that bad; does she make bad, humiliating choices, or is she just unlucky or too submissive? Put those thoughts aside for a second, because - kind of a spoiler here though many reviews mention this inevitably - the novel shifts gears in the second half (this section - perhaps the whole 2nd half of the novel? - is called Trust Exercise - as we now jump from a h.s. story about teenagers in and out of love some 15-20 years ahead to a young author doing a reading and book-signing, and we soon realize that the author is the author of the novel that we've been reading - and one of the attendees at the reading is one of her h.s. friends and thus the model for one of the characters in this novel. This could be interesting, though it all depends on what Choi does w/ this material. I have little interest these days w/ postmodern theatrics - is the "author" the author of this book or is the "author" a character? Where do we draw the boundaries between fiction and memoir?, etc. - but I do like the idea of a novel including a reaction to its own publication; in other words, there's a lot of potential if the young woman at the book-signing confronts the author/her old h.s. friend and tells her what she got wrong (or right). So far, though, this hasn't happened; what we get is a lot of updates on the lives of some of the characters; the central male figure, David, is now apparently a successful theater director in the same community (Atlanta?) in which the first half of the novel was set. I'm feeling a lack of direction at this point in the novel, and would like Choi to surprise me w/ something and to make her narrative decision - jumping ahead in time, calling into question the nature of fictional narrative itself - to provide a payoff and to give me insight into the lives of these characters.