I'm in the early stages of my first novel and I think that sex is almost needed. Writing about attraction and sexual impulses is just about the only aspect of writing that makes me uncomfortable to me. I don't want it to sounds awkward, out of place, or at all trashy. This fear is especially amplified by the fact that the first part of my novel takes place in a very conservative setting where sex means breeding, not sex. Do you have any advice concerning how I should approach "romance" portions? When do sex scenes make an auto-reject? Could you give source materials of novels that do sex well?
Oh, and do mainstream publishers care about homosexual relationships and sex scenes? I fear my chances of being published might be hindered because the plot currently involves a gay lead character.
I feel concerned about another aspect of the novel. It basically describes the ride and fall of this religion. Parts of the religion are hidden in books that the main character finds and reads. The character knows it's coming, but is it okay that I put what is contained in the book in a chapter placed before he starts reading it and when he is done? How often do you get this? Should I move these sections to the end of the novel?
So I'm going to try to answer this from the perspective of a potential publisher as opposed to the perspective of a writer. I think that would be more helpful to you.
1. As you no doubt have noticed, many many adult (and young adult, really) fiction that is not romance, erotica, or smut often contains sex. If this is a huge shock to you, go read more fiction. Any thriller with a male protagonist who has a sexy woman helping him should do. Publishers are not afraid of sex. The issue is how descriptive the sex is. Does it describe body parts using their proper medical names and in graphic detail, or is the entirety of the scene "he bent over to kiss her as he turned off the light"? Probably somewhere in between. Like in movies, how much sex is too much is generally something that's a judgment call for the editor, not because the editor thinks kids will be exposed to naughty bits (as concerns the movie councils) but because the editor might feel it distracts from the story.
2. No. The answer to your second question is no, we're not against gay protagonists for mainstream fiction. We just don't see a lot of it, because 90% of the country is straight, and straight people tend to write straight characters or disturbing mpreg slash fan fiction. There are a lot of great gay writers, some of whom don't write about being gay necessarily, or don't make it the central focus of the story but one of the plot points. Somewhere on my bookshelf is a set of lesbian detective stories, legitimate ones written by an actual lesbian who wanted to write queer thrillers. But we don't see a lot of these submissions, partially because there are just less gay writers than straight writers, and because it can be a smaller market depending on how central the homosexuality is to the story. I say, if you want to write it, totally go for it. I've had enough of smart academics solving mysteries, aided by sexy female lab assistants. There's no reason not to have sexy male lab assistants helping smart academics solving mysteries - and then, presumably, falling in love because of the intense experience they shared in that chase scene in the ancient Mayan ruins.
3. I didn't entirely follow your third question, but I think you have two potential situations: a situation where the reader knows the same amount as the character and a situation where the reader knows more than the character. (You can also have the character know more than the reader, a nifty dramatic device that can be annoying when done wrong) Whether you want to go in one direction or not is a question of suspense. If the reader knowing more than the character makes the character fall flat, then the reader will be annoyed and just start flipping through. If the reader's knowledge helps us understand the character's quest as they experience it better, go for it.