I grew up with them (same approximate age as Harry, still waiting for owl acceptance to Hogwarts). Agree with @JessicaJaleres that Fred’s death was the saddest.
Favorite book is probably the 4th (I think I read it at least 10 times growing up). Not a big fan of the movies because I liked imagining it better, but I’ve seen all of them.
Come to think of it, I probably could re-read the later books since I think I only read the 6th one once or twice and the 7th only once (HATED the epilogue, such a blah moment to end the series, actually I hate epilogues in Episodes too haha, your imagination should take it somewhere, not have the author spell it out IMHO).