YA can be a discriminative term; fiction that is written in the (casual) vocabulary and (short) sentence structures that the adult authors assume teens can understand, in settings that the adult authors assume teens can relate to, with teen characters (and sometimes very few adult characters involved). Plots are often stereotypical; I think there are two types, one is the realistic plot (featuring a terminally ill or suicidal girl is a common way to add drama) and the other is the paranormal plot (love and/or adventure with magic! monsters!).

Oh, come on. By the time you get to high school, your reading comprehension is as good as adults, if not better.

Here are some books that address youth's concerns such as sexual relationships, identity, dealing with adults' hypocrisy, etc. in a way that doesn't cater down to teens.
(Your parents might not like you reading these; consider reading in your room.)

Meanwhile, some jewels that deserve adults' attention are hidden in YA. Perhaps I'll make a list of those later.