You first must be granted liscence and then you are "given" the material that you are alllowed to work with. Thats usually how it works.

Not necessarily.

Most often, a publisher makes the decision on which books to publish, it's rarely the other way around but it does happen (if an author proves that there is a market for that book).

If you notice, most publishers have certain series that they fit books into (for example, Sams Publishing has "(Program name) Unleashed", and "How to Use (Program name)", and so on.

So, let's say the publisher want to do a book on Poser. They think about which series it would do best in, and then they seek authors that can write for those series.

The material that the book covers is pretty much up to the author ... the author prepares the outline and proposal, according to the guidelines that the publisher has for the series they are preparing. Unfortunately, a part of that proposal is figuring out an outline that will fit within the desired page count. Some books series allow for 750 to 1000 pages, but other allow for 250 to 500 pages.

For a program as complex and feature-laden as Poser, it is very difficult to to a thorough job in 250 to 500 pages. So you either leave out the basics that already appear in the manual, or you cover them in a way that is easier to understand.

Hope that clears up a little bit.