The theory behind tec diving (physics physiology etc) is pretty standard among all of the tec agencies. I think that is why you are seeing similarities between the Naui book and the GUE book.
The GUE Tech and Cave 1 books do not teach you how to be a DIR diver. The teach the DIR diver how to implement the tech skills (as mentioned above they are similiar) into the DIR approach. If that makes sense.
GUE fundamentals is the course to learn how to dive DIR. This course will teach you what is expected from a buddy, how to swim properly (trim, buoyancy, etc), how to ascend, descend, hold stops, shoot a bag, etc. The cave and tech courses then take those 'raw skills' and teach you environment specific DIR/general diving rules and procedures (i.e. line running, communication, gas switching, buddy procedures specific to the environment). as well as the reasoning behind the DIR principles that you are working towards/learning.
Aside from the configuration and philosphy, there isn't anything special that a cave course or tech course will teach you deferintely than a course from another agency (as far as skills and such, although you will be held to a higher and more exacting standard in the GUE course).
That being said, you can't teach someone this stuff in a book. The book is for theory specific to the application. The course is for actual learning of the way it's done.
For example, take a stroll around the 'net, you'll find many different examples of what people 'think' is DIR and GUE condoned, 90% of those examples are wrong or misunderstood. You don't learn to dive by reading a book, just like you don't learn to be a doctor reading grey's anatomy.