Defiance of the Fall book 13, just need a bit of a spoiler...

Just started book 13 and I just want to say I hate the 2 bodies situation. No matter how the story defends and justifies his situation, his core is technically a failure, well at least for now.

Honestly since book 7 its been hard to finish each book, I still love it overall, but this thing with the 2 bodies its really disappointing.

I just want to know this one thing, what book does Zac fuse his 2 bodies back together? Book 14? 15?