Muzza said:
Just stay far away from "The complete idiot's guide to calculus" (by Michael Kelley).
I would have to respectfully disagree, but then again, I am the author. Even though my book is not specifically written for a "scientific" audience (there are plenty of those already), it is still rather rigorous. If you're looking for more rigor, I just released "The Humongous Book of Calculus Problems."
The kind of book you need depends on your learning style. If you learn better by doing problems, then hit the Humongous Book. If you learn better when things are explained and put into layman's terms, then hit the Idiot's Guide.
There are people on this forum who like to disparage titles because of the series name. This is short-sighted. Many of these are the same people who would say "Don't judge me by my appearance, I'm really nice on the inside." However, they are apt to making "clever" and sweeping judgments under the blanket of anonymity online.
I am very proud of the Idiot's Guide. I worked long and hard on it. I went to many major publishers suggesting a calculus book like it, and none thought there would be an audience. They told me math people would disparage it without even looking at it, and that anything less than 100% rigor would earn scorn from group of people that love scornbread (my term). The Idiot's Guide people said, "What the hey," and gave me a chance. Apparently there is a market.
While it doesn't cover each topic using proofs, and is most certainly not as rigorous as a textbook, it's a good companion to use along side a more rigorous text. Of course, if you're into scientific texts, as one poster above suggested reading the textbook, then the Idiot's Guide is not for you. The vast majority of students can't learn calculus from a textbook. Just because it's not for you doesn't mean it has no value.