Book of Lost Hours by Hayley Gelfuso

One fateful evening, eleven-year-old Lisavet Levy finds herself trapped in the time space—a vast, enchanted library where memories of the dead are bound into books. As she grows up among the stacks, she discovers that government agents are infiltrating and destroying books to maintain their preferred version of history. Determined to salvage what seh can, Lisavet creates her own book of memories...until an American agent, Ernest Duquesne, arrives to stop her, setting off a battle over memory and truth that could change history itself.