A book about stopping time

Question

When I was younger like in 7th grade or something, about 6 years ago, I remember I picked up this book that was about time stopping. I don’t know if it was a series or a single book. I don’t remember the name or the author, except that I’m pretty sure his name was James but I’m not sure, but I do remember this:

It was about how two teens, boy and girl, (around 14 or 16) who were the only ones unaffected when the world and everyone in it stopped. There was a bad guy who I think was like from history. They teamed up to try and stop the evil guy and became friends. I think also along the way they found a group of “rogue kids” who were also unaffected. And I also remember the name of the girl which was Cassie and I’m not entirely sure but I think the boy’s name was Jack or something along the lines.

Answer 1

The first of the "Time Stoppers" books was published in 2016, and while the main character's name is not "Cassie", the author's name is Carrie Jones.

https://www.goodreads.com/book/show/26073154-time-stoppers

The book features a girl and boy named Annie and Jamie:

"Annie Nobody thought she was, well, nobody, living in a nowhere town where nothing goes her way. Day 1 at her newest foster home proves to be dreadful, too... and things get even worse when she's chased by something big and scary that definitely wants to eat her.

Luckily for Annie, not everything is what it seems, and she gets swept up-literally-by a sassy dwarf on a hovercraft snowmobile and taken to Aurora, a hidden, magical town on the coast of Maine. There, she finds a new best friend in Jamie Hephastion Alexander--who thought he was a normal kid (but just might be a troll)-and Annie discovers that she's not exactly who she thought she was, either. She's a Time Stopper, meant to protect the enchanted.

Together, Annie and Jamie discover a whole new world of magic, power, and an incredible cast of creatures and characters. But where there's great power, there are also those who want to misuse it, and Aurora is under siege. It's up to the kids to protect their new home, even if it means diving headfirst into magical danger."