The Six of Crows duology consists of Six of Crows and Crooked Kingdom.
Written by Leigh Bardugo, the books are set within the Grishverse (a few years after the events of the original Grisha trilogy).
It's not necessary to read the trilogy first, like I did, but I feel it's beneficial. You'll get a better view of the world and magic system, and the cameos of characters from the original series will be mean a lot more to you.
That said, I think the duology is better than the original trilogy. It's difficult to compare the two, though, since Six of Crows is essentially Oceans 11 meets Game of Thrones. The Grisha trilogy is more of a Hobbit-esque quest / adventure story.
In a nutshell... Imagine if the crew from Firefly was younger, and it was set in a medieval fantasy world rather than a sci fi western one.
I feel that any good Young Adult fantasy book has to contain the magical trilogy of good storytelling.
1) World Building
The Six of Crows duology has all of them covered.
We enter the grungy world of Ketterdam, a port city in a world speckled with magic users. Some of the city is respectable... but plenty of it is full of pleasure houses, gambling parlours, and unwitting tourists. It's a haven for the disreputable, and where everyone ends up when they're down on their luck.
Of course, this is where we meet our main characters.
Without spoiling too much, I can tell you there are six main characters (no surprise there)... Including Kaz, a vicious and brilliant mob boss in the making, and his right-hand girl, Inej, dubbed The Wraith for her ability to make her way around the city like a ghost.
One of the things I loved most about this series is how beautifully flawed and multi-faceted the characters are. The banter between them all is hilarious, and we learn a lot about their strengths and weaknesses (and what made them that way) as the story progresses.
The plot of the first book is essentially the crew attempting to pull off an impossible heist of an impenetrable fortress (I won't tell you if / how they succeed or not).
As you'd expect, virtually nothing goes to plan ... and somehow you find yourself cheering for these beloved characters, despite the fact that they're criminals.
Crooked Kingdom, the second book, is even more fast paced than the first. Somehow the stakes are even bigger, and the odds are seemingly insurmountable. Just when you think things can't get any worse, the plot throws you another curve ball which has you wondering how the heck anyone is going to survive.
The series has a well deserved 4.5 / 5 stars on Good Reads, and I highly recommend reading it!
P.S. Once you read it, you're going to want to get your hands on this limited edition mug, which is inspired by these books... and available for July only!