The Dark Tower V: Wolves of the Calla (2003) by Stephen King
Yup, this is my favorite Dark Tower book- so far.
It's concentrated and self-contained, even as it continues the main themes of questing and good vs. evil that run through the previous books. Here, a small farming community- Calla Bryn Sturgis- is preparing for a once-in-a-generation attack by unknown creatures. As had happened many times before, these creatures swoop in, take one twin from each pair in the community (most children born there are twins), and whisk them off to an unknown location. These children are ultimately sent back to their families, but with significant physiological and psychological problems. No one knows why they are taken, or what is done with them. But this time, instead of just letting the kidnappings happen, the people of Calla Bryn Sturgis are determined to fight. They ask Roland and his ka-tet (who are passing through their region) for help.
Roland, Eddie, Susannah, Jake, and Oy simultaneously help the calla prepare for the coming of the "Wolves" and make "trips" to New York to convince a bookstore owner named Calvin Tower not to sell an abandoned lot (which contains a very important rose) to the criminals for whom Eddie used to work when he was a drug smuggler back in his "when." Meanwhile, Susannah/Odetta/Detta realizes that she is pregnant with what is mostly likely a demon-child- what will happen when she gives birth is anyone's guess.
What makes this installment in the series so weird and great is King's continued blurring of the line between fiction and reality. The "Wolves," for instance, carry light sabers and sneeches, and are themselves modelled after characters from the Marvel universe. One of the characters in the calla finds a book in a cave that is about him, written by a man named Stephen King. And lastly, just outside of the calla lies a bunker with monitors and other equipment for the purpose of spying on its people. Why? And who is doing the spying?
More than the previous Dark Tower novels, Wolves of the Calla focuses on how we shape/perceive reality according to what we can understand about our place in the world. Its mash-up of many genres (western, myth, scifi, fantasy, etc.) calls particular attention to the porous barries between genres.