Books ca be helpful, but for me, a large part of training has to do with socializing and relationship building, so I find that going to a class is much more helpful. It helps to have another set of eyes watching. If i'm working with timmy to try and train him to "sit", it helps to have someone watch me as well to see if i'm teaching him "right".
(i'm assuming you meant behavior/obedience training, not potty training. . .)