I loved all the characters and the ideas that this series has with all it's twists and turns. I love the writing style of the author. Confusing at first with all the time skips back and forth from present day to the past 3 years. Though enjoyable nonetheless, but the bittersweet ending left me feeling kinda empty.
(Spoilers) You have all this build up, constant tension with Goddard trying to take over the Scythedom, Faraday trying to hunt down the Fail-safe and Citra and Rowan on the constant run from danger. Then Goddard has a quick un-grand defeat, the fail-safe doesn't feel as extraordinary as the build up felt like it should be, and Citra and Rowan are safe on another planet.
Now whatever happens after is up to our imaginations, which while yes is fun to theorize what would happen next or leaves the author room for another book. It's hard to be satisfied with an ending with so many loose ends.