I'm not yet done reading this one as the holidays have been something of a distraction.  I picked this up as suggested reading while looking for books related to the Memory Palace.  I am in my 30's and pursuing and engineering degree which is very math intensive and while I have a great calculator I want to sharpen my ability and solve problems more quickly.  This book has been a pleasant surprise and a joy to read thus far.  I have always enjoyed the challenge of performing math problems in my head and feel that Arthur Benjamin's methods have helped my structure and organize the way I approach mental math.<br><br>I would recommend this book to any one who wants to keep their mind and math skills sharp.  If you can memorize your basic multiplication tables you will be amazed at how much you can build on those basic table very quickly.  I plan to teach my kids this method once I finish the book and master the skills.