A Midsummer Night in Oz: Book 6 of the Mari Fable Mysteries - Emily Fluke

Two worlds.
Fates intertwined.
And we accidentally killed the man trying to separate them. What in the fairy tale hell have we done? With Sherlock Holmes dead, it is up to me to seal the rift between Storyland and the human world before the war between fairy tales spills over into San Francisco and my family become the casualties. Not to mention the millions of other innocent people that villains and monsters will hunt. Thankfully, I have my husband by my side and a trick up my sleeve. Okay... it isn't so much a trick as it is a theory.
If Sherlock Holmes was right and we find the source of the error in Storyland, we can rewrite the ending. Then we'll cross our fingers that the revision sends the characters from Shakespeare's plays and Oz back to their original tales, effectively sealing the rift and saving the world. But there are bigger powers at play. Bigger than the Keeper of Stories. Bigger than Oz and the human world...this strange and mysterious Author of All might destroy everything we've built.