"The Art of Fair Isle Knitting: History, Technique, Color and Patterns" by Ann Feitelson, 1996, has quickly become an essential part of my knitting library. Included is the history of Shetland/Fair Isle knitting up until the present day. The chapter on FI techniques is great and she makes a great case for using the long needles with the knitting belt. A variety of different ways of throwing the yarn are shown along with a fantastic page demonstrating and explaining why one colour is carried consistently over the other and how the decision which yarn to carry where makes a huge difference in how the pattern looks when completed. She gives such a good lesson on changing colours, finishing ends and of all things, increases and decreases in a FI patterning (I was surprised). The chapter on colour in FI knitting is extensive and very helpful for me who is rather colour-challenged. The garment recipes are lovely and for the first time I've found FI jumpers that I'm keen to make for myself.
I highly recommend this book for someone who is interested in stranded knitting. Be warned: it's rather addictive!