The Infinity Ring is essentially a young adult science fiction time-travel adventure book series; three young teenagers are sent through time using an infinity-shaped time-traveling device, and their mission is to fix time. It was written by a team of writers, most notably James Dashner and Carrie Ryan.
Dak Smythe, Sera Froste and a young adult named Riq are the stories’ main characters. The best book, in my mind, is Behind Enemy Lines; the characters travel to the year 1943 and are sent to Spain on a secret mission. If they fail, the Allies might just lose World War 2. Here’s the twist: in these books, neither side won the war. Both completely destroyed each other, which allowed the SQ, the main villains, to gain power and control of the world.
In the end of this book, they succeed and the Allies invade Sicily, effectively allowing a series of events leading to the fall of the Italians during WW2.