First Among Sequels (Thursday Next #5) by Jasper Fforde

Preloved book, secondhand book, used book

It's been fourteen years since Thursday pegged out at the 1988 SuperHoop, and Friday is now a difficult sixteen year old. However, Thursday's got bigger problems. Sherlock Holmes is killed at the Reichenbach Falls and his series is stopped in its tracks. And before this can be corrected, Miss Marple dies suddenly in a car accident, bringing her series to a close as well. When Thursday receives a death threat clearly intended for her written self, she realizes what's going on: there is a serial killer on the loose in the Bookworld. And that's not all--The Goliath Corporation is trying to deregulate book travel. Naturally, Thursday must travel to the outer limits of acceptable narrative possibilities to triumph against increasing odds.