This book definitely has certain charms, with vivid characters and some nice insights and turns-of-phrase. But I did find the title to be substantially misleading. There are some almost scholarly passages about yarn and knitting history related to victims' clothing from crime scenes, but the majority of the stories are about supernatural occurrences in faded, old-world and other-worldly parts of San Francisco. Think Sunset Boulevard meets Stephen King. The not-quite central character is a knitter, but she too fades in and out of the stories. The narrator's voice switches from first to omniscient unexpectedly, and there are many gaps in the story lines.
All that said, there is an appeal to the title character and potential for serious development. But this book is not about a "yarn woman" in the sense that I was anticipating from the title. It's essentially about supernatural occurrences related to crimes in San Francisco. For me personally, the actual textile-related material was a disappointingly minor side theme.
So, as long as you understand what you're getting, it does have some interesting elements.