Probability Without Tears: A Primer for Non-Mathematicians.
I wish every textbook were written exactly like this book. The book is almost pocket-sized but is packed full of explanations and examples of how to do basic probability calculations. The author talks to you through the book, not just teaching, but understanding what you're going through. He knows when he's overused an example or when you're frustrated. It's perfect teaching. By the end of the book, you're putting it all together and it makes so much sense.
Probability, binomial distributions, permutations and combinations. He makes it all easy, and provides enough practice problems that you feel confident, and exams to test what you've learned.
It looks like it's out-of-print. I got it used for like $4.00.
This book actually gets 5 stars out of 5. I wish every textbook was written as well as this.