Excellent sequel! I sometimes worry about sequels (especially movies) not living up to the original's quality, but this one did.
Aiden took over as Commander and a "new" villain surfaced, more terrifying than the last. The story flowed really well from book one to two, with returning characters and some new ones as well. Plenty of action, lots of funny banter, and a mysterious hero who became one of my favourite characters.
There was a bit more focus on the Creator in this book, which I'm not used to as I'm not religious, but it was handled well and there were strong messages of inclusivity, equality, and forgiveness that all religions and spiritualities would be able to relate to.
Glad the ending was left open for a third book. It was a satisfying ending, but there's a little cliffhanger to keep it going--my favourite sort of ending to a book.