This is NOT a novella.
The Assassin and the Captain is a short story/scene that takes place in between Throne of Glass and Crown of Midnight.
Part 1: http://www.fantasybookaddict.com/2013...
Part 2: http://toofondofbooks.com/2013/08/the...
Part 3: http://www.paranormalindulgence.net/2...
Part 4: http://www.alexalovesbooks.com/2013/0...