Ruin and Rising is the end to the Grisha trilogy. Start from the beginning and read all 3 through to the end.
This ending is EPIC and ALL i could've dared to hope for.
While weaving the final tale of our Sun Summoner Alina, Mal, Prince Nikolai, The Apparat, The Darkling and the Grisha, Bardugo does an absolutely wonderful job of throwing you for loops, all while tying up all loose ends.
I finished this series completely satisfied.