There have been plenty of books on mathematically-based effects, but there are very few books available on the proper presentation of those same routines. Hidden Numerical Forces by Thomas Henry is a valuable and much-needed book on just that topic.

Thomas Henry breaks the process down piece by piece, so that not only do you know the techniques and proper presentation points, but also why other presentational avenues are not taken. Take a look at the PDF preview of Hidden Numerical Forces (opens in a new window) to see the first half of the first chapter, which discusses the 37/68 ploy.

He starts by talking about the basics of the technique in each chapter. One of the best parts about this book is that it often gives better explanations of the techniques than do many non-presentational math magic books. Also, when possible, credits to the originators are given in detail. Once the reader is on solid ground concerning the techniques, it's time to move onto presentational exploration.

I don't use the word “exploration” lightly, either. The author takes the time to lead the reader through less effective ways to present each force, and what makes each avenue more or less effective than it can be. In the process, you're not only learning about how to properly analyze presentation, but how to get inspired from the mistakes. It's not just one approach per force, either. Thomas Henry explores multiple presentations for each routine, as everyone is going to find ways that work better for their presentations and their audiences.

I'm amazed at the thoroughness of the included forces, as well. Especially interesting is the “Half 1089 Force”, which I first ran across in the October 2002 issue of MAGIC Magazine, in Jim Steinmeyer's “Two Dictionary Test”. Instead of using the full 1089 force, this is a way of effectively stopping in the middle to take advantage of a little-used property of the numbers generated after the first step.

Hidden Numerical Forces is valuable not only for the lessons it does provide, but also for the inspiration it gives you in learning how to explore presentations in your own routines. I highly recommend it!