A stirring backstory to virtually every major character in Twin Peaks (except Laura Palmer and Dale Cooper, who got their own books) by the show's other creator, veteran TV writer Mark Frost. It provides a comprehensive history of the town of Twin Peaks and puts the series' paranormal elements in the context of the last 300 years of occult lore, which doesn't provide any answers to the show's mysteries (I'd be annoyed if it did) so much as show how and where they resonate with mysteries throughout history.
My only quibble is the strange decision to make Doug Milford, a very minor character from the TV series, essentially the book's main character, investing him with far more gravitas than his humorous one-episode appearance would suggest. But the backstory invented for him is very interesting, so I can't complain.
Highly recommended for fans of the show.