If you want to master Photoshop, a complete course can be found in the books recommended below. Think of this as a multi-book master class.
Some of these wonderful books are out of print but you can still find used copies at Amazon via the links below to the individual books and to my photography store.
If you don’t already have a good, solid background in Photoshop start with Lightroom and Photoshop: The Essential Books before diving into the series of books listed below. If you are a true beginner, start here: The Best Basic Introductions to Elements, Photoshop, and Lightroom.
ADVANCED SKILLS AND TECHNIQUES
Your image processing begins with how you process your RAW files with Adobe Camera Raw (ACR) in Photoshop, Lightroom, or Elements. Your best guide to ACR and RAW is Jeff Schewe’s book, The Digital Negative: Raw Image Processing in Lightroom, Camera Raw, and Photoshop (2nd Edition). What you do with your RAW files determines how much or how little you can do with the file in Photoshop. You maximize your possibilities by making the right choices in ACR. Make the wrong choices, and you have limited what you can do later on. While you are at it, if you want great looking prints from your digital files, get Schewe’s book The Digital Print.
After that, you can jump into color correction with the two books by Dan Margulis. I would suggest you read Professional Photoshop 6: The Classic Guide to Color Correction first, followed by Photoshop LAB Color: The Canyon Conundrum and Other Adventures in the Most Powerful Colorspace (2nd edition).
Dive into digital retouching with the two books by Katrin Eismann as the lead author. I would suggest you begin with Adobe Photoshop Restoration & Retouching (3rd Edition) before moving on to Photoshop Masking & Compositing (2nd edition).
It doesn’t matter whether you read Margulis or Eismann first, or if you read one book by Eismann and one by Margulis before moving on to the second book by either author, but I do recommend you start with the camera RAW book by Schewe).
Reading these 5 advanced books, plus whichever basic-intermediate books you choose, will provide a master course in Photoshop. You will be able to do amazing things. Have fun!
If you want to go the extra mile (as if the above list of books isn’t enough, read Photoshop Channel Chops by David Biedny, Bert Monroy, and Nathan Moody and Welcome to Oz by Vincent Versace. If digital black and white photography is your thing, From Oz to Kansas by Versace is an essential read.
You can learn more about these books in the series articles linked below.
The Mastering Photoshop Series
The “Mastering Photoshop” Series – Series Overview
Buyer’s Guide Series
The Mastering Photoshop Series is part of a larger series of over 60 articles that guide you to the best of all things photographic. The rest of the series is here: Buyer’s Guide: Recommendations For The Best Photography Equipment, Software, Books, Magazines, DVDs, Online Photo Labs and More.