When in doubt, reading is fundamental.
Any geek like me will tell you, when you’re up against a new technology, the first thing to do is grab the right O’Reilly book.
So let’s start off with the obvious:

The plus side is that you’ll find in this book a lot of really good dirt on getting your money’s worth from adwords. There is a Parental Advisory here, though. Some of the information may be slightly out of date. Some of the topics may drift too far into the tech or sales lingo for your comfort level. And while it’s a credit to O’Reilly’s usual thoroughness, there is a certain amount of content in here that is probably just too esoteric for non-developers.
You can hardly fault them for putting too much material into a reference book, though, right?
Check it out if you’re new to adwords. It’s the best, most complete “Starter Kit” you’ll find, in my opinion.