One of Our Thursdays Is Missing by Jasper Fforde
This is the sixth in the Thursday Next series, and probably reading the earlier ones is needed to understand a good number of the plot twists. Not that it's always easy to understand after reading all of them, any more than they were; lots of literary humor and cerebral jokes. And it's impossible to review this one without spoilers for the earlier ones.
For one thing, it's a different Thursday Next as the heroine -- the one from The Great Samuel Pepys Fiasco -- acting as the Thursday for the first five books. BookWorld gets reformatted, geographically, but as the inside of a globe, not the outside of one. Thursday plugs along, welcomes some new neighbors, tries out an understudy, and one day, is warned on a train (bookhopping is now considered low, since you can travel) that one of their Thursdays is missing. She also has something sneaked into her pocket.
And that is just the beginning of her adventures, featuring the Men in Plaid, a clockwork butler, imaginary friends, cryptic messages, a trip to the RealWorld, metaphors, a clown army, and a boat ride up the Metaphoric River. And the plot is truly amazing in its conclusion. Although there are hints there may be more adventures ahead for this Thursday Next.
I like the character switch. Then, I generally approve of character switches in series, on the grounds that there is only so much character development you can wring out of a character without undermining the happy endings of the previous books. It works rather well here. The written Thursday Next had already been set up so that her development lay wide open for this work.