So a lot happens in this conclusion of the Fever series (well conclusion for now..).
Mac thinks she loses someone she wasn't even sure she cared about. Now she realizes that this person means a lot more to her than she's willing to admit.
And she goes all "hulk" on the world. She's going to do everything she can to get that book to make life different so she can have that person back again.
Later on Mac learns a lot about the person she realizes she loved. A lot more she never thought possible. I don't want to give anything away, but I am seriously so glad with what happened between Mac and this "person."
Anyways, overall it was a very good ending to this book. It leaves it open to wear there could be other books later on, or there could be a spin off series, which I do believe there is one. And almost all of your questions are answered about Mac, and Barrons, and everyone else. Well almost everyone else. There are still a few things we don't know. But otherwise I really enjoyed this book. I am extremely happy with it, and I highly recommend this series.