Second Chronicles of Illumination

When an alien invasion threatens the existence of all the knowledge in the universe, eighteen-year-old Johanna Charette and seventeen-year-old Jackson Roth must rely on their wits, guts, and pluck to save the fantasy-come-to-life world of the Library of Illumination.
It wouldn’t be so bad—all right, it is bad but it would hurt less—if Johanna and Jackson weren’t the ones responsible for breaching the portals to a dozen distant worlds. Now, outside forces are causing shock waves in the space-time continuum, and if that isn’t awful enough, someone from another dimension is trying to steal a book of powerful spells created by a very famous wizard.
At first, traveling to other realms in a time machine seems like a fun perk. However, discovering some inhabitants want to obliterate the teens doesn’t leave them with a warm, fuzzy feeling. Instead, they find themselves forced to sacrifice their own welfare and the safety of their loved ones for the greater good.