I have found lots of useful references about fiber, spinning, and knitting. I have provided links for more information/purchase. Please note that I do not receive any kickbacks for this, and also note the book format to make sure you are on the one you want.
The Knitter’s Book of Yarn – Clara Parkes. Clara also has a website with great info and discount codes for her online classes at Craftsy.com. See below.
The Knitter’s Companion – Vicki Square This is absolutely indispensable. I refer to it all the time.
Clara Parkes: The author of The Knitter’s Book of Yarn, Clara also has a newsletter and a website with great info and discount codes for her online classes at Craftsy.com.
Socks 102: For more techy info about knitting socks, this great article on Knitty.com is by Kate Atherly, who wrote the book Custom Socks, linked above.
Lion Yarn Stitch Finder: This Stitch Finder page provides detailed instructions and images of popular knitting and crochet stitches. It is an excellent resource for all kinds of block construction, animal and flower shapes, and so on.
400 Knitting stitches by Alicia Salarza – An online e-book with many lovely stitch designs.