I should start off by saying that I absolutely love Leigh Howard Stevens' Method of Movement for Marimba. In fact, I've written about it before (click here for details). One part of my admiration for this book is that the concepts can be applied to other instruments, and indeed to life in general. However, there is one area in which I think Stevens could have expanded, or at least clarified - the preparatory stroke.
I take exception with two of Stevens' statements. The first is that the preparatory stroke is a waste of movement. The second is that it is proven unnecessary because multiple rapid strokes are played with piston movements. Therefore, a piston stroke is all that is necessary.
The preparatory stroke CAN be a waste of movement. However, I believe that it is useful for (surprise, surprise) preparing to play. It can be used (often in conjunction with breathing) in an ensemble setting. It allows the performer to not only prepare themselves for the tempo of a piece, but to give a clear visual cue to other performers that the percussionist is about to play. Multiple rapid strokes are played with piston movements. However, they do not need preparatory strokes because they have actual, audible strokes preceding them. Therefore this is not a persuasive argument for completely eliminating preparatory strokes.
From reading Stevens, one could get the impression that preparatory strokes are NEVER acceptable in playing. I disagree. The physical act of hitting the right notes is only one part of percussion performance, especially in an ensemble setting. Maybe you agree with me; maybe you disagree. At the very least, consider whether preparatory strokes are acceptable. And remember that no matter how much you admire a book, you are free to disagree with portions of it.