This book is excellent, just let me say that to start. I have read/used many books and videos over the years, but never come across one that is so straight to the point. That said, this is not for beginners. The terms used can be confusing at times, especially if you just skim over them as I know it is common for a lot of us to do, myself included. I always skim through a new book when I first get it to have an overview of what's in store. However, once you sit down and start reading this, it starts to make a lot of sense. I think that is one of the main things about this book...it makes you think! This is critical in nei kung/qi kung/taoist alchemy methods. You really do have to take your time reading this though, it can be very technical, and I have to sometimes try and look up some of the terms used in other source materials. A familiarity with taoist terminology is vital here, very very vital, so if you don't know about what I mean when I talk about Qi, Shen, Yi, Kung, Dan Tien and such...and things much deeper, you might want to start with something a little simpler. I have found a couple of other books that proved useful, primarily these two...
This book by Damo Mitchell is also excellent, and my primary go to book. It takes you from the very basics up through enough advanced stuff to keep you busy for years. If you can only afford one book on Nei Kung, his is the one. No doubt. What is nice is he's a westerner and writes clearly and concisely, in a language that is understandable for a western audience.
This book is also good, Stuart Alve Olson gives you a nice solid start in terms of an introduction to the more intelectual side of Taoism. This is the first book I ever read, and it really did give me a very nice understanding of basic terminology and what all the strange words like Qi, Jing, and Shen really meant.
Without going through those, I would not have understood this one at all, purely speaking from and intelectual standpoint. You have to have that understanding before even hoping to apply any of this in a practical manner. Wang Li Ping is way way more advanced than any other modern practitioner I have ever come across. If you have not read "Opening the Dragon Gate, Making of a Modern Taoist Wizard" which is the story of his training, I highly recommend it. The stuff in it might read like a wu xia novel, but believe me I know that once you get far and high enough in training, this stuff IS possible. I firmly believe this, I've seen and experience some really strange things over time and can attest to the truth of what this stuff. Well worth the time to read and try out.