The Lunar Chronicles . Absolutely one of my favorites ! It's a clash of Disney princesses, Indiana Jones and Star Wars! Must read Marissa Meyer
Two-book series/duologies seem to be gaining popularity in YA! Check out some of these duets! Except Treatment is a trilogy not a duet.
Teh Chronicles of Narnia - C S Lewis
The Ruby Red Trilogy Boxed Set - Kerstin Gier, Anthea Bell
You have every book in the series proudly displayed in your house. 19 Undeniable Signs You're Obsessed With "The Mortal Instruments" Series
20 series to read if you loved divergent
Booktopia has The Fallen Series Boxed Set by Lauren Kate. Buy a discounted XD of The Fallen Series Boxed Set online from Australia's leading online bookstore.
Want to Read- Matched Trilogy (Ally Condie) these are really good and not very popular. I would recommend these to anyone.
Snow Like Ashes is one of my favorite series!