I must have 30-35 books on presentations or PowerPoint. Some of them are good (such as Cliff Atkinson's new book), but many of them give the kind of advice that may help someone learn how to use PowerPoint, but will not teach them how to incorporate the slideware in a way that makes the media transparent and the visuals powerful and appropriate.
When it comes to making good use of visuals, most of the advice out there centers very much on the functions of PowerPoint instead of what makes for great visual communication. The books, when they do discuss visuals or PowerPoint, advise us to do what is commonplace today. Such as how to insert an MS clipart image, or what size typeface to use, or that we should use no more than seven lines of text and seven words per line. Many even advise how many slides to use and how many minutes per each slide!
When speaking of "typical" business presentations in the business world today, those which use the aid of PowerPoint may be visual disasters and generally ineffective, but they are so usual and commonplace that it has become "normal." Few complain — Seven sentences per slide? A screen bean thrown in for good measure? No one ever got fired for that, right?
Part of a more "Zen approach" to presenting well, if you will, is learning to give up what you have learned about making presentations in the era of "PowerPoint Culture." The first step, then, is to stop letting our history and conditioning about what we "know" (or thought we knew) inhibit our being open to another way, a much better way of presenting.
After a seminar, someone usually asks what PowerPoint book I recommend to help them make their visuals look much better. I reply that they do not need another PowerPoint book, but instead they should read up on the basics of graphic design and visual communication for ideas as well as inspiration. I like this one for a very good introduction.