Interweave Press sells this book directly from their website, which is a good thing, because it's a very useful and affordable introduction to socks.
The 18 patterns in the book are all top-down sock construction, but even a toe-first enthusiast will find a lot to love about this 120-page paperback.
The first four chapters in the book detail the history of socks, starting from before they were even knit. The fifth chapter outlines the anatomy and basic construction of a sock. The sixth details a "classic" sock pattern, but offers choices between 7 different ways to make a heel and 8 ways to make a toe. All of which means that, even if you just knit from that chapter, you could create 56 different pairs of socks, before you even get into the other patterns Nancy Bush has written out.
Of course, since it's an Interweave Press book, the photos are great, the illustrations are clear, and the index is extensive. As a bonus, two whole pages of bibliography are in the back of the book, so you can sock nerd out to your heart's content if you want to go out and find sources like A Visual History of Costume: The Sixteenth Century and The Windswept Isles.
And, as a bonus, and just because I'm such a fan, you should read the Yarn Harlot's "Top Ten Reasons Why Nancy Bush Is So Cool I Can Hardly Stand It."