The Knitter's Book of Yarn: The Ultimate Guide to Choosing, Using, and Enjoying Yarn by Clara Parkes is an informative and entertaining guide to everything you need to know about yarn.
The Knitter's Book of Yarn is written by the editor of Knitter's Review (http://www.KnittersReview.com), Clara Parkes, who has been reviewing yarn, needles, and all things knitting for years.
It includes a thorough discussion of the 4 major types of fibers used to make yarn: protein fibers (wool, cashmere angora, etc.), cellulose (plant) fibers, cellulosic fibers (rayon), and synthetic fibers (nylon, acrylic, etc.). Clara writes about the characteristics of each kind and where they come from. More importantly she explains the properties of each kind of yarn and what type of knitting uses are best for them.
Clara also has a whole section of the book that covers how yarn is made from the major mill to the microspinneries and everyone else in between. Plus she discusses the different processes used to dye yarn.
Finally, in the third section of the different plys of yarn (single, two-ply, tree-ply, four-ply, cabled, textured, boucle, brushed, and chenille), she has 40 knitting patterns that take in the best features of each type of yarn.
I especially liked the two-ply Baby Soft Cardigan (page 91), the four-ply Princess Mitts (page 173), and cabled-yarn Cabled Headband (page 187) by designer Jennifer Hagan of Figheadh Yarnworks. The baby cardigan has an unique slightly asymmetrical front placket that doesn't require a button band to be knit. And the fingerless gloves have a beautiful cable pattern on top.
Amy King has several nice patterns including an angora cardigan, Vines Cardigan (page 103) and a cabled-yarn vest, XOX Vest (page 183).
Other designers featuring patterns in the book are: Adrian Bizilia, Cat Bordhi, Teva Durham, Jackie Erickson-Schweitzer, Norah Gaughan, Amie Gavin Glasgow, Bess Haile, Lana Hames, Shelia Janury, Elanor Lynn, Tara Jon Manning, Gina Wilde, and Margaret Klein Wilson.
Clara Parkes has included several of her own patterns including a lovely Butterfly Moebius shawl done in a cabled-yarn.
What I especially enjoyed about all the great patterns in the book is that in addition to listing the yarn used in the pattern, the book also has recommendations on what type of yarn to use for substitution.
Two patterns from the book are available for free, Maine Morning Mitts by Clara Parkes and Princess Mitts by Jennifer Hagan
Errata for the patterns is available on the Knitter's Review website.
The finally section of the books is a great reference that any knitter could use. It includes how to care for handknits and special considerations to keep in mind for each type of fiber. There are couple of invaluable charts, one on figuring out Wraps Per Inch (WPI) and the other listing the standard yarn weight system. And the abbreviations and technique section is invaluable.
Overall, The Knitter's Book of Yarn is a must have for any serious knitter who want to knit better finished garments. It gives all the information you need to make better buying decisions of yarn and wonderful patterns to use the yarn with.