I second the motion. Calculus Made Easy is unique in that it explains calculus based on extensive verbal description that attempts to get at the underlying intuition, rather than abstruse terminology or runaway deductive logic. It's the only book that I've ever seen that comes straight out and says that integral dx means "the sum of all of all little bits of x". It makes a useful supplement to a textbook since there is little unnecessary material for the student to get lost in. I learned from this book and love it.

I would suggest going out an getting a book on Interaction Design, such as that by Sharp, Rogers, and Preece. If you look over the diagrams and the chapters you should get the gist of it. This book is used in introductory graduate Human-Computer Interaction courses.