Question: Which book is more a beginner to learn to program in c++ (or GML) and more fun: "Game Maker 8 Cookbook" (available for pre-order), or "The Game Maker's Companion" ?

Answer: 
I created a game in Game Maker long ago, and was frustrated with the lack of control over many of the game elements. They try to take the programming out of game making. So I'm afraid you won't find Game Maker to be much help if you're trying to learn C++, or really programming in general.
I would recommend going with [Beginning C++ Through Game Programming, Third Edition](http://rads.stackoverflow.com/amzn/click/1435457420) if you want to achieve your intended goal.
Both books will teach you Game Maker's drag and drop, neither will teach you C++.
Im not sure if the cookbook teaches you GML, though i know the companion does.
Both books have their own style of teaching. So on that matter, purely subjective.
The Cookbook is slightly cheaper (thought not much)
The Companion is out already.
The companion might (i'm not positive) require you to get the game makers apprentice as well.

Overall i would say companion. The sooner the better, and it will teach everything you need to get started. The Game Makers apprentice might be needed first though.

And regarding C++... Well thats a totally different area. If you want to jump straight into it, neither of these books will help. However if you want to learn the basics of using logic to do things before delving into the details of the language, well it might help to learn GML first.