Well I'm pretty sure the best book you can get to learn DarkBASIC is the official book located on this website, but if it is too expensive or you need more help I recommend the binary moon tutorial also located on the this website. Also if you have any special questions about something that isn't answered in any of the other things I advised, then just ask them on the forums like you did now, just don't ask for help for something really stupid like I'm a newcomer and I want to make the next Halo, or Half-life, or another really complicated game.
Cocacola and Pepsi aren't that differnt. Deal with it.