The Book Beast's Shadow. Jitter Jumpers, #27

Thirteen-year-old Cyrus lives for The Chronicles of Eldoria. In the safety of her book-filled bedroom, she can traverse moonlight-forged kingdoms and obsidian mountains, far away from the "muted reality" of her own solitary life . But the lines between fiction and reality are starting to fray. The ink on the pages is shifting, turning heroic knights into skeletal mockeries and vibrant meadows into decaying bogs .
As the "Book Beast" begins to bleed through the parchment and into her room, Cyrus realizes that the most dangerous monsters aren't the ones in the chapters, they're the ones she's been trying to read her way around.