"Ubik" by Philip K. Dick
Woah, this book was a journey! Even though the last quarter of the book is simple action, the ending is very on-brand for PKD. Just as we'll never know whether the bladerunner is an android himself, we won't ever know why the money is this way at the end of "Ubik".
I came across "Ubik" by accident, searching for the best PKD books. "Ubik" was #1 on one of the lists, even though I'd never even heard of it. Not going to lie, a thought occurred to me many times while reading that the book might represent my own reality, which was quite disturbing. Partially, because the book popped out seemingly out of nowhere (and that's one of Ubik's properties), but also because of the ads for Ubik printed at the beginning of every chapter.
A solid PKD book, packed full of peculiar concepts and futuristic mumbo-jumbo, just as I like them!