Nobody tells you that when you publish a book, it becomes a license for total strangers to say outrageous things to you that yourself could never imagine saying to anyone. I'm not just talking about people who've actually bought your book; even people who haven't read your book feel encouraged to share, based on what they've gleaned from friends, reviews, the Internet, or ESP.
At first, when you're on tour, it's surprising, then tiring -- but eventually it's funny, and sometimes even offers you material for your next book.
All the comments on this list have been offered to me or author friends of mine.
I liked your book, but I hated the ending.
Your characters shouldn't be so nice.
Your characters should be more likeable.
You need more sex in your books.
There was too much sex in your book.
The book doesn't make sense unless there's a sequel.
You used too many words I had to look up.
Too bad you're not better known.
It'll never sell.
My bookstore doesn't carry any of your books.
I found some typos in your book -- you should fix that.
I'd like you to write my book.
What's up with that cover?
Can you tell your agent about me?
You have a way with words.
You need to put a nice lesbian in your next book.