I've devoted much of my life to studying sexuality and I know what the research says. More porn and erotica—the twisted sisters of visual and written sensuality for the express purpose of arousal— equals less real sex. That doesn't sound exciting to me. It sounds very "vanilla." Here are a few sources for you to begin your own study of the impact of porn and erotica on the sex lives of humankind.
Keep in mind that more has been done to study porn than erotica, but I believe they are similar and function the same in terms of brain chemicals and consequences. Beware. These sources can be a little bit steamy, so don't click for more unless you're mature enough to handle it.
Most research on porn and erotica follows the impact of men. However, SELF Magazine's study on the sex lives of women revealed that "if you're regularly using [porn] to satisfy your sexual needs alone, your habit could end up replacing actual sex," and that "a woman may also worry that after watching the actresses in a porn video, a partner will judge her body negatively."
New York explored The Vanishing Male Libido in a rather racy article that revealed that when it comes to porn and masturbation versus a real woman, a real woman has a hard time winning the war in an addicted man's brain. A man tends to want less real sex when he's consumed by erotic pictures.
This Italian study revealed that men who used a lot of porn had trouble becoming aroused.
In the TED talk below Philip Zimbardo explains that porn creates an adrenaline addiction (as opposed to a substance addiction). While a substance addiction makes a person want "more", an adrenaline addiction makes a person want "different." This means that porn and erotica will always lead you way from what you already to know (read: current partner) to a different sexual experience to sustain arousal.
A myriad of studies out there would point to this same conclusion. While porn and erotica seem to provide an initial jolt to a mudane sex life, they eventually lead you away from having a great sex life with a partner. That's a risk that I don't think is worth taking.
For a more comprehensive view on how the brain is impacted by the casual treatment of sex, be sure to get a copy of Hooked: New Science On How Casual Sex Is Impacting Our Children by Dr. Joseph McIlhaney who founded the Medical Institute For Sexual Health.