2. If you'd published your fanfic online like everybody else, I would not have had to read an entire chapter to determine that your Mary Sue was stupid and obvious, because I would never have gotten there.
3. It is entirely possible that people who are unpleasant to their romantic/sexual partners are interesting in other ways, but when you don't show me any of their traits but being unpleasant to their romantic/sexual partners, it makes it hard for me to summon up any damn to give.
4. Do you know why we sometimes write dialog instead of paraphrasing it every single time? Go away and find out before you write another book.
5. I know that it is not unrealistic to write a completely self-absorbed character, particularly one without much life experience. But that doesn't make them any more fun to read about, particularly when you, the author, don't seem to realize that this is not how everybody is. When your protag moans that they have no friends and I think, "Give me $5 and I will tell you why," this is not the road to a long and happy reading experience.
6. You know what's worse than writing alternating viewpoints where I only care about one of the viewpoints? Writing alternating viewpoints where I don't care about any of the viewpoints.
7. Biography is an art form. It is an art form that does not require the writing of twee, precocious dialog to put words in your famous subject's 10-year-old mouth.
8. Have you met any actual New York street toughs like the ones in your book? No? This "write what you know" thing: it is not perfect advice. Its limitations are rather severe. But "write what does not make you look like a complete idiot" is a good place to start.
9. It is your prerogative to hate people like me and think we are all awful. It is my prerogative not to read about it. Neat how that works, huh?
10. It turns out I don't really care what Famous Historical Personage #1 wrote to Famous Historical Personage #2 about the food at a party they both attended and I didn't. I thought perhaps my dislike of collections of letters was something I had outgrown. Nope.
11. This is a personal idiosyncratic thing as well: I am a really, really tough sell for books about tiny people. I don't mean human beings of medically abnormal stature. I mean people 3-12 inches tall. As fantasy conceits go, I can't think why this one is such a loser for me, but it really is.
12. If you are going to write an historical novel for teens, the fact that it is historical fantasy does not excuse you from doing your research. (Do I even need to say that the fact that it is for teens does not? I had better not need to say that.) And if you got the street names right and the basic gender roles and limitations of the period very wrong, you did not do your research. It's not just the bits you think are important about the period. It's the bits they thought were important about the period.