This is an excellent primer on yarn. The author describes the whole process of yarn from the fiber level to the finished spun yarn. She provides a great survey of the different types of fibers and the inherent nature of these fibers and how it affects your knitted piece. It's kind of the "Good Eats" of knitting. She goes into some scientific detail but not too deeply -- just enough for what you need. Very easy to read. I borrowed this from the library and intend to get my own copy as a reference. She also has patterns for projects for each of the different types of yarns and also has a primer in the back on how to take care of the objects knitted. Great reference for the beginner knitter intimidated by the different types of yarn.