A good explanation of knitting two socks at a time on two circular needles, although there is a better one in Queen Kahuna's Crazy Toes & Heels Socks by Mary Ann Beattie. Beattie's is a non-ISBN self-published book with profuse illustrations. You could also try 2-at-a-Time Socks by Melissa Morgan-Oakes
In Bordhi's book, there is a basic sock in three sizes (child's, women's, men's; all medium) and ten other patterns, with a sampling of styles--color patterning with yarn floats, instarsia-in-the-round, duplicate stitch, lace, felting, and reverse stockinette patterning. A variety of heel styles are presented within the patterns. My biggest objections are that the patterns each call for a specific yarn and the fact that the book occasionally reads like an ad for Addi Turbo needles. There is also information about converting other patterns to this method.