I have only read this book in its hefty hardcover form, but it's also available as a paperback.
Anne Macdonald's book, published in 1988, is thorough, interesting and a very fun read. I don't tend to re-read books that don't involve patterns or recipes, but I first read this one about 10 years ago. Even though I knew I had read it before, I picked it up again this year, because I thought it could still teach me more.
It's a very big, serious-looking book, but don't be scared off. Anne's writing style is engaging and very readable. There is a huge bibliography and source list in the back for the reader who wants to delve more for themselves.
The book came about before our latest renaissance of online knitting, Knitty, etc., but that doesn't reduce its scope as much as you might think.
I really can't recommend it heartily enough.