I'm not saying Rowling is the bestest and greatest ever writer, but she knew (knows) how to capture most people's attention. She used attention to details and threw in all kinds of information throughout the books. She even managed to throw in some history in the form of mythology.
Some of the 'classics'? They put me to sleep every time I try to read them. It's not all of them, no, so I don't lump all 'classical literature' in the same category. I also do not discount modern writers because their works haven't been around long enough to become 'classic'.
Now, Twilight, that series made me want to gouge my eyes out, but it got my daughter reading so I'll give it a break.
I had an instructor tell me the difference between what most people call literature and modern writing was about 75 years and usually the author's death, probably in some horrible way after living a not so nice life.