So I'm definitely in the minority in this but I don't crazy love the way these books are written - as transcripts, chats etc. Like, it's fine, I can still read it but I'd rather it was just written as a normal book and, in Gemina in particular, I found some pages physically hard to read - there's a lot of dark grey text on black backgrounds and the like so you need to be in good lighting (and have pretty good vision) to read this without straining your eyes. I frequently had to move to bettet lightning because I just couldn't read what was going on. There also some places where the words were all over the place and it's not immediately obvious what order to read them in which is annoying. 
 The things that redeemed Illuminae for me were the characters and the plot - I really liked Kady, Ezra and Aidan, I liked the spaceship setting, the way te main enemy was largely absent and yet had such a great effect on them. I thought it was clever and I was invested in the characters and their story. 
 With Gemina - not so much. The characters were fine, I did like them, but I wasn't attached to them like in Illuminae and I found the plot far less interesting. 
 (view spoiler)[ When Ella and Nik 'died', I wasn't really bothered. I also don't like when characters fake die - like, if you're going to kill a character off, commit to it, or I'm never going to believe your characters are really dead and I'm noy going to have an emotional response to it. It just feels kinda cheap, I guess? (hide spoiler)] 
 I know this seems like a really negative review but I didn't hate Gemina - I did give it 3 stars after all, I just felt pretty mediocre about it. It kept me engaged enough to read all 650-odd pages, though I was willing it to end after about 500. I did like the characters some, and I like the way the plot is going - enough that I'm intending to read the third book. I'm hoping to see more of the Illuminae characters in it, although I'm also expecting two new protagonists - I do feel that new characters in a series help to keep it interesting. 
 I would also like a cat. It is set on an actual planet so that could be a thing, right?