This book is excellent for going over the basics of all different types of cooking, techniques, and principles. It's extremely approachable and has a ton of pictures. I highly recommend it if you're looking to expand your repertoire :)
Anything by James Peterson. Cooking.
I think subscribing to cooks illustrated as well. I still get it and learn something new every time on the science side.
Get Cooking by James Peterson and Ratio by Michael Ruhlman. Pick a recipe that interests you, and make it.
Try Cooking by James Peterson. It's got all kinds of detailed instructions...