Secrets of Mental Math is in a league of its own. Its clear, succinct, and well paced. If you're familiar with the "For Dummies" series (like I am, I admit!), the book reads at about the same level.<br><br>Its worth purchasing because the shortcuts aren't anywhere else on the Internet. (I think the author actually discovered some of the mathematical shortcuts, himself).<br><br>One word of caution: make sure you feel comfortable with each technique before moving on. I didn't do this the first run through, and had to go back.