if you really understand the story i.e. Easter eggs hidden in the story and then reflect, you'll realise you have to be a little older to understand them. (e.g. things hidden in the 'room of requirements' mentioned in Harry potter books), almost as if JK Rowling expected you to read it again After the first time to fully understand the concept she tried to convey. (I read the whole set age 9 but when I re-read it age 15, I realised the little things I missed out such as the entire Harry potter family tree from the peverell brothers and that majority of the characters had some relation (lineage) with the 3 brothers.
Majority of those who answered your question do not really read books as if they were immersed in the book. Judging by the lack of knowledge of HP books but claim they've read it means they were looking at words with no imagination... People who actually read books are getting rare these days...