Once the characters got into their relationship, I didn't like them nor their lack of chemistry. 

I loved Ava and Maya, and while the initial plot was enticing, I felt very little attachment to Letty and Jon. There was very little chemistry between the two, almost zero build-up, conversations between them felt stilted and awkward. Personally, this novel seems to need a refinement pass to cut some of the fat and make the gems of the story shine.