I really like those books because they taught me how to be fair to my dog. When I first got my pup I was kind of a crank and yank trainer... To teach sit I pulled up on leash pushed down on but... Those books along with a litany of other sources helped me understand how unfair I was being with Ajax. They improved his obedience 100 fold while at the same strengthening our bond.
I would also recommend Ivan Balabanov's "Obedience Without Conflict" to anyone who plans to do competition anything with their dogs. They are dvd's and can be a little pricey but I have found them worth their weight in gold!
(Since they are dvd's it isn't much weight, but you guys get the expression!