Knitters who know me know that I love a good reference book. I savor detailed explanations, carefully labeled diagrams, and knitting books just stuffed with information. Here are two such books, both of which have recently arrived at the shop.
In Circular Knitting Workshop, Margaret Radcliffe gives expert guidance on the technique for which the book is named. This includes several different methods of knitting in the round: using a singular circular needle, two circular needles, and four or five double-pointed needles. Radcliffe then arranges quite a lot of knitting knowledge around this technique, explaining how gauge, charts, and finishing techniques function in circular knitting, as opposed to a flat knitted piece.
Most useful of all, perhaps, is her section on converting pattern instructions from flat to circular. This is a question that comes up at the shop all the time; a knitter admires the look of a pattern, but would rather work seamlessly in the round than sew flat pieces together. Circular Knitting Workshop is the best resource I've seen for making these kinds of changes to a pattern.
Meanwhile, The Sock Knitter's Handbook focuses this same kind of technique-teaching attention to the particular craft of knitting socks.
Charlene Schurch and Beth Parrot have put together a great resource, with schematics and instruction for both toe-up and top-down socks.
Many heel and toe variations are explained and clearly illustrated, with different colors of yarn used in each different step of knitting. This helps to highlight the construction of the thing, the process that gets you to the product.
Come by the shop to stick your nose in a book or two, for that, too, is one of the great pleasures of knitting.