You can take a look at Lynda.com they have a lot of courses on AdWords. I used them to learn a lot of Adobe products and it was super helpful - I've watched some of the AdWords courses though not all of them - and they were pretty good.
Additionally, you can pick up some books about AdWords which are really helpful. While some things do change over time, the basics are still the same - what I learned 10+ years ago still holds true today, there are just new tools and new features you can utilize. This book is a pretty good one - I keep a copy close by to reference from time to time.
Other than that - AdWords is a lot of on the job training, which is great if you're not using your own money to learn.
I only read 2 books on PPC and read the PPC Hero and WordStream blogs (checkout PPC university). I started my company soon after and I'm currently managing my own campaigns, spending thousands each month. Go to Amazon and get:
Ultimate Guide to Google AdWords: How to Access 1 Billion People in 10 Minutes
I only read the first one, but I wish I'd read the second one by now. Instead I read Ultimate Guide to Pay-Per-Click Advertising. It's good, but there are a lot of weird little mistakes and confusing topics. YouTube is also your friend.