Since you asked about books:
A great book to also consider is Mark Elling's "The All Mountain Skier: The Way to Expert Skiing".
You should be able to find it at either Borders or Barnes & Noble. It breaks out skiing into various components such as carving, moguls, powder etc. and has a "tool box" approach to working on technique. It also covers gear.
The problem with books is that while they can be an interesting read, books don't really work that well for a lot of people. You can read how to do something correctly but you often can't actually see yourself doing it. On the slopes the difference between what you think you are doing and what you are actually doing can be dramatic. That is where an expert instructor/coach can make all the difference.
I would really think about doing a multi day clinic like Epic Ski Academy, if you can. Small groups, expert instructors and the multi-day approach is the best way to significantly improve for many, in IMHO.
Skiing in many ways is counter-intuitive. There are some activities like in-line skating, soccer or ice hockey that correlate well with skiing but most activities do not. This means a lot of new muscle memory learning needs to take place. The multi-day clinic approach can be very valuable in this regard.
The big problem with self-taught skiing is that you can get good at doing the wrong things well. This will soon limit your progress- a lot of what the so called intermediate rut is about. If you are one who can read and then execute great. However, when it comes to skiing, many if not most probably don't fall into that group.
PS. I've attended two ESA's as well as having read a lot of books.