I bought this book to help with the GMAT. I wanted it to help me do basic math more quickly in my head without using that pesky notepad they make you use as scratch paper. The book makes a great deal of sense, is very easy to follow, and you can comprehend his approach to math and why it is quicker his way. You do need to practice though otherwise you will revert to the standard way that you learned growing up. I also have noticed that I am using the tricks from the book to entertain friends! Fun times!