Don't get me wrong, this is a good book... but definitely not what it is advertised to be. This is not the ultimate guide to understanding overall differences between yarns so you can choose the appropriate one for your project, or match the project to an appropriate yarn. There was a small amount of this in broad strokes, such as: protein fibers being warmer than plant or synthetic fibers -- 3 and 4+ ply yarns being better for structure and stitch definition than 2 or single ply -- yarns with less structure have more drape -- etc. But in then end, the majority of her advice/guidance/direction boiled down to: experiment. Feel the yarn between your fingers, let your hands inform you about the yarn, try out swatches with different needle sizes and types of stitches; let the yarn tell you what to do. I'm not kidding - this is the summary of the "Putting It All Together" section at the end. In multiple places throughout the book, she recommends buying one skein of a yarn you're considering, and experimenting with it in order to decide what to use it for.
I understand some of this is due to the nature of the product itself - there is great variation in nature, and you can't simplify it down to "wool always behaves like this," or "alpaca is always great for this" - even within one species of sheep, there will of course be an abundance of variety on amount of crimp, staple length of fibers, etc. I get that, and that's part of the beauty and appeal that keeps fiber enthusiasts endlessly enthralled with every new yarn! And this doesn't even begin to account for the varieties when you start considering the numerous blends on the market, which a majority of yarns are.
However, I would have appreciated a book that was a more practical, results-oriented approach to understanding the differences between yarns. This turned out to be a more sensory, exploratory approach that reveled in the subtleties and myriad differences changing one component can introduce. If you are familiar with Myers Briggs, you will understand when I say this is a great book for "S" types - but not so much for "N" types, which is what I am. I thought this would be a top-down, big picture framework approach to understanding yarns, and placing the nitty-gritty details into their home within the overall framework. Instead, it was an overwhelming traipse through a jungle of details, one after another, without any of them coming together in a cohesive fashion to create a bigger picture. The only "bigger picture" takeaway I got from this book: this author loves yarn, its myriad varieties, and loves to experiment with them all and see how individual ones work up. And again, there is nothing wrong with this. If I had been looking for a book to vicariously enjoy marveling at the differences from one fiber to the next, this would have been great. But I was looking for something from a more bird's-eye view, so I could have a more general idea in my head that wool is usually good for this, while alpaca is usually great for this, etc. If I slogged back through the book, pulled out little comments here and there strewn throughout the text, and re-categorized them according to qualities such as warmth, elasticity, drape, structure, etc., I could maybe develop such an overview framework. But that is what I understood the book was supposed to do - I didn't buy it just to do this myself! Rrrgh.
Again, I don't want to bring this review completely down and leave people thinking it was an awful book, because it wasn't. The author does a great job of giving a wonderful sense of enjoyment and exploration of various yarns, and there are many beautiful patterns in the book. But I feel it was really sold as something different than what it is - I came away more confused about the varieties of yarn, not less. And that was the exact opposite of what I was wanting from this book.