For @BWN_7 (from @amieshmamie's list). My Cousin Marcella is eight years old and recently started reading the Harry Potter books, my Aunt messaged me before letting Marcella start to ask basically the same thing you did! Here it is in list form, hope it helps! Starting with ten, instead of 24, haha!
  1. The first book starts when Harry turns eleven years old, and each book follows him for one year. They were written to age with the characters/with the target audience.
    So, while your son might be old enough to start the series, I would try to read a book ahead of him and decide with him whether he's ready to take on the later books. There are some resources like "Parents guides to Harry Potter" but most are written by extreme Christian conservatives that think it's all devil worship so I recommend just reading ahead, you know your kids best, and what they'll be able to handle/have questions about. Or you'll be ready to talk to them about harder things.
  2. That being said, it can teach kids a ton.
    Like Eric mentioned in his comments, the later books deal with things that parallel what we're seeing in our culture still today. There's been some fascinating research into how ready Harry Potter has helped shape a generations feelings on huge social issues. It can teach kids valuable lessons (perhaps subconsciously) about love, death, power/authority, friendship, racism, elitism, and much more.
  3. You'll fall in love with it as much or more than your kids will.
    J.K. Rowling is an incredible writer and crafted a universe that is compelling even if you aren't the "target audience". The first couple books might feel a little childish but even still, they're amazing and you'll zip through them. And of course, some of the social/life lessons that the kids don't necessarily pick up on, you'll see plainly, which makes it a great read for all ages.
  4. The Gospel allegory is strong.
    Without giving anything away, it's not as blatant as The Chronicles of Narnia, but it's more direct than Lord of the Rings. Not sure if that would come up at all in your family but it is something to be aware of. I wasn't allowed to read these as a kid and then when I did at 18 I made my Mom read them to show her there's nothing for conservative Christian parents to even be concerned about.
  5. The story arc will be familiar.
    To fans of Star Wars and Lord of the Rings especially. It's not like it's some new original story, it's a different setting of course but there's a lot of similar elements and characters.
  6. A lot of the "Controversial" stuff that Jo Rowling has said/done isn't present in the books.
    Again, may not apply, but there were things Jo Rowling said in some cases years after the books were done that caused Christian conservatives to freak out. Don't pay attention to that, they don't come up in the books.
  7. If you read ahead, write down some things you think might come up as your son reads.
    I don't have kids, but when I was a kid I remember having lots of questions about things I read, and when Mom and/or Dad had read the books they could obviously more adequately discuss topics with me, whether small things or deeper questions that might arise from reading.
  8. Read all of the books before watching any of the movies.
    My cousin watches each movie after finishing the book and I think it's better to wait and do it all after. Let the power of reading and imagination do their thing before letting the films dictate how they imagine parts.
  9. Have fun with it!
    Obviously dressing up and going to premieres or book releases at midnight isn't an option anymore. So I recommended to my Aunt to invite Marcella's Harry Potter fan friends over for theme nights, make Harry Potter recipes, play Harry Potter games, etc.
  10. Follow along on Pottermore.
    It's a website designed by Jo Rowling that allows the reader to follow along with the story, they can get sorted into a Hogwarts House, get a wand, etc. A lot of us did the few things and never sign in again but if you keep up with it while reading that could be pretty awesome. Plus, incorporate it into the theme events with friends! Have them each take the test but don't share the result and then do a "sorting ceremony"