Harry Potter is a book for all ages. It merges real life, with fantasy. Each book as all the good characteristics that make up a story. Some can't get into it, and that's understandable. Not everyone likes books that have to do with wizards,witch's,giants and many,many other creatures, including giant spiders and trolls.
Many people also don't like the simplicity of the first 2 books. Well, let me tell you the books grew with the readers. By the time you get to the 7th book a complicated plot with a mixture of characters, and characters intentions and personality's are revealed. It creates a world where every character has there own thought's and actions. The characters aren't flat, many are rounded out by the 7th book. Sure it takes 7 books, but we only get the information Harry gets, so we only find things out when he finds them out.
Over all it is a series that is "real". Many books I've read, have certain characters that are brought out, but many are ignored, and the other character's are ignored. J.K Rowling new what part each character was going to play when she wrote it, so each character was made and there line developed so foreshadowing for characters is in each book, even if you don't realize it till the event happens.
Not to be compared with LOTR or Eragon
LOTR:Quest to destroy a magic and evil ring, world, characters and setting are original, and is a category on it's own
Eragon:A Boy Who finds a Dragon Egg, one of the last, and because of that the King want's him killed. Set in a distant land with some magical creatures. original to say the least (Very interesting, also, lots of plot twists)
Harry Potter: About a boy who survived a all power full killing curse, cased by the most powerful dark wizard of all time. The series outlines his quest to stay alive while the powerful dark lord is trying to return to a body to finish him off for good, and take over Britain. Also, a tale of how to survive school. You follow the story by watching Harry, the boy who lived. Sounds bad, but in reality is a original work, that is ingenious