Literary porn is pretty hard to discern. A book can officially be non-erotica, but in reality it is soft porn. Sex scenes don't make a book porn. I have been reading the Song of Fire and Ice series (aka Game of Thrones) and there are sex scenes aplenty in the series. They are stupid sex scenes. (Ironically the television series takes out certain sex series and adds in others seemingly at random. They took a book with a good number of short sex scenes, eliminated a bunch, only to add in others that are even worse/explicit. So I am not watching that series anymore) But to some extent they give you some insight into a character and have something to do with the plot. To some extent even Twilight was soft porn in the way women read it. And that book didn't even have much (if any, I haven't read the series and never plan to) sex in it. This 50 shades was inspired by Twilight afterall.
I have struggled with this issue since around age 10 when my reading level was high enough that I needed to be wary of content. I think you have to be captured fairly young to find much of the erotica sexy. Phrases like "dewy center" just make me think of incontinence. Many, many Christian women read romance that is essentially soft porn without so much as a blink of the eye.
The problem I have with soft porn romance is that I think it is (in it's own way) much more dangerous than actual porn. Soft porn can not spice up a marriage in any healthy way just like regular porn can't. Soft porn and erotica can cause a woman to wish and desire an idea that is unachievable. A man that actually behaved like Christian Gray (I think that is the character's name in 50 shades) would be an awful partner. He would be an even worse husband and father. A woman can read these books and go to bed "in the mood" and actually have sex with her husband physically but will not be thinking of him when they are having sex. Emotionally/spiritually she just isn't there. That is dangerous for a marriage. The man will think everything is OK because she is having sex with him. But she could loathe him and just be using him as a living/breathing sex toy. That sounds good in theory to many a man. But no one wants to simply be used for sex in a marriage, man or woman. Everyone wants that connection that is deeper than sex when they are having sex. Otherwise you feel like you would after eating an entire cake. You would enjoy the flavor while eating, but afterward you just feel sick and sort of hallow. Not to be crass; but sex (and especially orgasm) is when a person is the most vulnerable. That vulnerability can't be there completely unless people trust each other. So if you think your marriage bed isn't up to par it isn't because you need to "spice it up" it is because you need to be more honest in your communications outside the marriage bed. You don't need to read/watch other people having sex to do it right yourself. That would be like watching NASCAR in order to learn how to drive better. The two are similar, but NOT the same.