Improve your maths! Book

Man, I wish I had read this book BEFORE undergrad. In this book, Velleman does three things:
* describes basic concepts in Logic
* gives common proof strategies, with plenty of examples
* dives into more set theory, defining functions, etc

He does all this assuming the reader is NOT a mathematician-in fact, he does an excellent job of explaining a mathematician's thought process when trying to prove something.

I highly recommend this book if you feel uncomfortable reading and/or writing proofs, since it will make the following math books much more enjoyable to read!