Mercedes I would be considered a young adult, due to my age, and no I did not find it one bit 'erotic.' To me it was and absolute page turner though, and I could not put it down.
This answer contains spoilers… (view spoiler)[2,3,4 does have lots of erotic e.g cole wanted to do stuff after ail is cured of her sickness and 3 and 4 with lots of sexual stuff i them so basiclly number 1 is at beginner and as you read through the books it builds up to number 3 and four being advanced (hide spoiler)]
A. Yes, yes it is. It's not adult level of erotica, but it is. There's a lot of sexual language used in this book. For example, Cole saying to Alice if she didn't do what he asked her to do he would spank her in front of everyone (don't even get me started on how that's abusive behaviour, I know).
Kanta Nobody in this book goes beyond kissing, though Alice's best friend mentions that she has had sex. There is a strong religious undertone and it is repeatedly stated that Alice's virginity is important and she must have a very thorough talk with the man she wants to give it up to.