One series that I'm working on the first couple chapters of book three is An Ember in the Ashes. The third book is A Reaper at the Gates by Sabaa Tahir. It's been two years of waiting for book number three. When I started reading this series, I couldn't hardly wait to finish the first book. I'm reading book number three a little slower as I reacquaint myself with the characters. I'm already starting to pick up speed as I am remembering events that led me to love these characters and their story. If you want to read a really good series, and haven't tried An Ember in the Ashes, I recommend it.
Another series that I thought was finished, but now has another book coming soon is from author, Leigh Bardugo. If you liked the series Shadow and Bone, you will look forward to King of Scars. This book comes out in January and will continue the story of Ravka, and secrets, and dark magic.