All the Louise Penny books
This would be a tie between the Harry Potter series (which I didn’t read until adulthood) and The Thirteenth Tale. Both stand up to re-reads and have much to offer after multiple visits but the twists and “wow” factor will never quite be the same as the first time I read them.
“Little Women”, it’s the book that caught me and gave me the desire to read, and 50+ years later I’m still reading!
This is a tough question because I love to re-read, and do it all the time. But I think it’ll probably be the Selection by Kiera Cass, since I hold such great memories from when I first read it.
The Raven Cycle series by Maggie Stiefvater! I absolutely adored it & would love to experience falling in love with the characters again.