Hi there,
Welcome to DBPro! you'll find you can do so much more with it than with Game Maker.
You don't say whether you have any experience with programming games, and assuming you don't then you'll want to look into the basic framework for producing them (i.e the game loop and functions).
You can do a basic search on the net for lots of articles on the theory of how games are programmed - very useful and you don't need a knowledge of coding to following them.
Book-wise, you could try the 'Beginners Guide to DarkBasic Game Programming' (Harbour & Smith) which is a very good intro into the basic DB/DBP commands and game structures. You could also try 'Hands on DarkBasic Pro - Vol 1' which states 'Fundamental software design and implementation is also covered' (not used it myself).
Also, if you've not already - have a go at the PacMan tutorial by ScouseKnight. Its a fantastic download which shows you how to program a version of PacMan and assumes you are a total beginner. It comes with a PDF 'Manual / tutorial' explaining how everything hangs together.
Hope this helps,
