the Dummies book will help you with most things. It's not incredibly complex, just a matter of knowing what you want to do with a given photo and then finding out how to achieve it. Cropping, sharpening the image, removing colour casts etc are all fairly straightforward. There's some jargon involved: burning means making darker, dodging means making lighter and "unsharp mask" is (sooo obviously!) to make sharper.
I've got something called Photoshop CS3 Extended, which has about a million functions I don't understand and will never use. I just ignore them.