I may be able to help out a bit in this area. I'm a ASE certified mechanic (engine and manual transmission), and I have been working on cars for 25 or so years. Currently though, I teach high school English, so do what you will with this info.
First of all, nothing can replace getting in there and learning by doing - the same as in brewing.
I would recommend, if you aren't already doing it, to start doing your oil changes, tune ups, and maintenance. Any good guide, such as a Chilton's, as has been recommended, can guide you in this.
If you have the room and a couple hundred bucks get an old VW bug. This is the most simple and easiest to work on car ever built - plus when you fix it up it will be cool. It doesn't matter if it runs or not as long as it is mostly complete.
Brew a good German style beer, and take it apart, and wonder at all of the little parts in which you have no idea about.
Then, buy The Complete Idiot's Guide for Volkswagens. Put you car back together, and marvel at you new found abilities.
Even if you don't buy the car, buy the book. It is both entertaining and incredibly informative.
As with anything else, everything you read is just theory until you do something with you knowledge, but if I had to recommend just one book, it would be this one.
Feel free to post or PM me questions as you get going; I love talking cars and beer. Good luck!
PS: If you are not married or want to get divorced, tear into a car you currently rely on for transportation.