Amie Kaufman and Jay Kristoff did a wonderful job developing the plot. On each page, there was a new surprise that was completely unexpected. Gemina held my interest throughout the entire novel. The authors did a remarkable job of developing the characters. I felt that I had personally known all of the characters throughout their lives.
I really enjoyed the humor aspect the authors included in Gemina. I would find myself crying due to the amount of laughter a few words had caused. I particularly appreciated the character of Ella Malikova. I also really liked Nik Malikov's humor and Hanna Donnelly's humor, Ella's humor is what really got me laughing. Ella has a very sarcastic and witty sense of humor that I found hilarious.
Gemina "is unlike anything that you will probably ever read. The story is completely told through journal entries, emails, online chats, medical reports, maps, interviews, other reports, and several other forms of media. I absolutely loved that the authors didn't use the traditional format and styles of writing, but instead used forms of writing, that you would never suspect to make up a whole entire book." (A description from my review of Illuminae)
I highly recommend reading Illuminae, the first book in the series, before reading Gemina. Gemina would be somewhat hard to understand in parts if you did not read the first book and know the back story.
I rate this book 5 out of 5 stars. You can read my review for Illuminae here