Bests & Worsts Reviews from Amazon

More than a book of numerical parlour tricks, but less than a satisfying immersion into the world of numbers. Having watched videos of his work, I was very impressed with Benjamin's speed and fluidity with numbers, as most people are. He certainly knows his subject and clearly enjoys it. But I feel he has yet to write a good investigation on the subject. I don't know how Michael Shermer's, whom I respect, added to this, but it certainly wasn't in bringing focus to the work. The first third of this book is gold. Sure, you can find much of it online for free, but it's presented here clearly and in an organized fashion. You'll notice that in a lot of the rave reviews, however, the reviewers mention that they "haven't finished the book, but can't wait to do so." I doubt many of them have, and it's not their faults. The book becomes a slog half way through, especially if, like me, you tend to take copious notes and try to really tackle the book like a course in mental mathematics, which it really isn't but on the surface presents itself as the sort of practical tome that will guide you through a better understanding of number theory and computation. The problem is that the authors get a bit carried away. You expect methods that will simplify mathematics or lay the complex groundwork for mentally calculating numbers with minimal effort in the long run. Or maybe just learn some neat tricks. But Benjamin is the type of mountain guide who gets sidetracked at every bush, shrub, running squirrel, bird sound, river and cave he encounters. For every easy road you set out on, Benjamin exclaims, "but you can also do this!" and dedicates a long chapter to various methods that are simply "the long way around". Yes, it's fascinating how casting out nines and elevens works, but do you really need a long explanation of how it works, mapped out diagrams and exercises, etc? The criss-cross method of multiplication works whether you're doing three, four, five, or ten digits. It's actually convoluted and doesn't exactly fit the title of the book. Imagine a book called "The Secrets of Reading", written ostensibly for the layman who may or may not love reading, devoting an entire chapter to decoding and memorizing backwards acrostics and anagrams in epic poetry written in obscure meters. I said that it's a slog for the serious student, but it must seem interminable for the person with only a light interest in what Benjamin is doing. The fact of the matter is, most of this isn't what Benjamin uses for his "lightning calculation" - it's stuff he happens to find interesting. In fact, I myself found better, simpler, more intuitive methods freely distributed online for many of these operations. Some that surprised me Benjamin didn't touch on. Ultimately his digressions are too much for the casual reader and lack enough real theoretical depth that would satisfy a devout student of mathematics. Imagine a carpenter who could hammer 100 nails in under a minute who then proceeded to show you 20 different methods for hammering in a nail or two at a time while throwing in tidbits about the lives of famous carpenters and carpentry styles throughout history. You'll either want to skip the hundred methods and concentrate on two or three that get the job done, or you'll ask to hear more about the history of carpentry but skip the 100 (often redundant or similar) methods for hammering with household objects. This is definitely a book you'll want to skip around in. Too bad the table of contents isn't obliging.