I'm sick of books that promise you that with just a few easy tips you'll be a great presenter overnight. In many cases I wonder if those authors have ever given a presentation. "What to say when . . ." is clearly written by someone who's been in the trenches and who appreciates the fact that presentation skills need lots of work - and why you need to have ways out of the tricky situations. In many ways it's like being with a small group of top presenters swapping war stories round a dinner table; the attitude is just as important as the information.
Second, this book actually gives you hope that when something bad happens in your presentation you might well be able to recover the situation. When you hear of how experienced speakers saved the day you will stop reacting to setbacks with total panic and instead think "How would the Walters deal with this?"
From the presenter's point of view, the most important message in this book is almost lost in the introduction. In a sidebar by Nate Booth, he makes the point that we'd rather not know - that sooner or later, something unexpected IS going to happen to you. I see so many presenters adopting a formal and distant approach in the hope that everything will go well, and then collapsing when things don't go according to plan. If you accept that nothing is perfect, you'll be taking the first step to relaxing in front of your audience - and giving a much better presentation.
The book is also readable for amusement. There are many examples of how to use humor to defuse tricky situations, and of course many examples of accidents that in retrospect are hilarious. My favorite is the story of the guy who skipped down the aisle to receive an award for running a department with the longest accident-free record. The inevitable happened, of course - but in a way that's much funnier than you could imagine. What was that? Oh, you'll have to buy the book to find out.
I think by reading through the entire book, you get a good feel for what is appropriate and inappropriate, and can then "wing it" if you haven't gotten a memorized response at hand.
As a public speaking professional, I will keep this in my collection, and review regularly, just in case!