Too much text and ... bla bla bla ...

You have to start with the game type you want :
RPG, FPS, Platform etc ...
you have to think on the ideas , the new gameplay, what will motivate the player ...
Than think in the graphic style ... the style of textures ...
And begin on some first level structure, put areas of interest, things to discover etc ...

Well if you have played a lot of games , you can easy find what agme you played and found amazing levels ...

I don't see the book interest .. too too much text instead of pictures ...
I would want to say, before diging on some design, find first what game style and ideas you want to make ...