An interesting question. I believe that the most valuable information a reader can get out of a magic book should be the answer to the holy question “Why did the author do it that way?”.
In my publications in German, I detailed a lot of my thoughts behind the tricks and some reasons I have created them or solved this way. In a magic book, this invisible part of the information is an essential element. You will learn a lot more if you concentrate less on the technical issues but shift your attention towards the ‘why’. It is the same in theatre — the character’s motivation and inner conflicts matter for the observer. The invisible things behind the scenes are the exciting and valuable things to go for in magic books.
The vast majority of magic books deal with a diversity of tricks and techniques. They are beautiful to read, and I enjoy a lot of them. But still — they are technical books, an instruction manuals. And most of them don’t answer the holy question.
The most interesting part is to learn about the creator’s thought process. That way, you can apply the particular form of thinking to your thinking and are not stuck to special tricks or techniques only, which forces you to merge into a clone of the other performer. Copying and replicating other people’s material is not the way to originality. You can apply that thinking to your work, and therefore different tricks or routines. This is of much more value than sticking to other people’s technical solutions.
All of this is the reason I had to change the traditional format of magic books a bit. Instead of the usual “effect, requirements, method, performance and afterthoughts” structure, I will describe my thoughts, the problems to be solved and the way I hit upon the hacks, first. After that, s short rundown of the actual workings of the routine should suffice. This might be an unconventional way to write a magic book, but hen — it is called NOTAS, and it is in agreement with the way I tackle magical problems in my head — and in my notebooks.