Some of the HTDM are pretty good - the marker one is worth paging trhough in the bookstore at least, and shows several different ways to use markers. The Costume Encyclopedia is good in that it shows normal everyday clothes from several angles and with folds, and the Couples one gives good advice on how to draw two people physcially interactiong (in more ways than what you're thinking, I assure you. XD)

They're all worth paging through in the bookstore to glean tips from. They're just not good in the actual drawing part. They're the "...For Dummies" of the manga world.