The Readers

Sapphire Rose Wood is an ordinary high schooler who loves fantasy books-especially Keeper of the Lost Cities and Percy Jackson.
One day, a mysterious man shows up in her home, saying he wishes to recruit her for an organization called "The Readers".
Sapphire discovers that Readers can travel into a book and that the man wishes for her to be the guardian of KOTLC and PJ.
Sapphire gets excited initially, but then she realizes that you can die inside a book and never return to Earth. This makes Sapphire scared, especially since she finds out that a rival organization called the Nevers is trying to make sure that things get wrong in the plot of the books by placing stuff from other books into a book.
Join Sapphire and her team as they travel through the books.

KOTLC characters credit goes to Shannon Messenger
Percy Jackson characters credit goes to Rick Riordan