Harry Potter series.
Harry Potter did many things right. The world building was fun. Like the Bible, (that's right, directly to comparing HP to the Bible) it created a world that could very well exist in real life, but even if it did, we'd never have a way to prove it. That's Urban Fantasy done right. There could actually be a fantastical Wizarding World right under our noses, and the foundation of that world is keeping us muggles from discovering it, or remembering it if we happened to find out.
Even as an adult, reading the first book which was written for 11 year olds, I barely feel like I'm being talked down too, if at all. (even without understanding that I am over two decades beyond the target age) It's written simply, but not stupidly. Lots of children's books come off as if they're explaining something to someone who is stupid, instead of someone who is just young and still learning a lot of basic things. There's an important difference, and it's a very difficult line to ride.
Harry is a great every-man character. He allows pretty much anyone to project themselves onto him, while not feeling like a completely blank-slate. He still has a strong personality and feels like his own person, without ever alienating the reader. Despite the hardships, the reader want's to be Harry. (generally speaking of course)
Sure the books have their flaws, there are some awful plot devices, time travel was introduced, but then 'welp, we shouldn't do that again!' But they're so much fun, and the adventure is so varied, and well paced, that it's a blast to read, and read again
The "horror" part is reading back as an adult and realizing how scarily f**cked up it all is.