A few years ago, I was approached by 3dtotal to do a beginners tutorial for Photoshop Elements. I chose to paint a simple sci-fi scene, explaining my usual work process in text, accompanied by images. It contains all sorts of useful information for beginner digital artists or anyone who's interested in digital art in general. Tools, composition, colours and more are all covered in a simple and understandable way. You can see a preview of the book here:
https://shop.3dtotal.com/beginner-s-guide-to-digital-painting-in-photoshop-elements.html#t1