I'm turning 30 this year and got into the books after the third one. My grandparents bought my little brother a copy of the first one for Christmas the year it came out and it took me a while to pick it up and give it a shot. After that I was hooked. My husband and I would order the Amazon delivery for the day it came out (I attended one midnight release party). One year, I think it was for the fifth book, we were away on vacation (hour and a half drive away), left our vacation so we could get the mail delivery of our book, drove back to vacation and read Harry Potter the rest of the time.
We always purchased two of every book and would sit on the couch and read and discuss. I'm a faster reader than my husband and it would irritate me that I'd have to wait for him to finish a chapter :)
While the movies weren't great, I did appreciate putting faces to the names and learning how to pronounce Hermione!