Would the books in the series AI Game Programming Wisdom make a diffrence if I buy #3 instead of 1 or are they like books where you have to read all of them in a row, I didnt know if they're the same thing with added stuff or not?

No, the books are arranged like a series of articles so you can pick up any book, open it at the start of any chapter and read some great tips straight out of it.

Saying this, I recommend buying AIGPW2 for the review at the beginning of current AI methods and techniques. AI is an evolving science, and the artful use of it requires knowledge of many topics. The opening chapters in this book are some of the best summaries I've ever read, and there should be enough material in the book itself to get you off the ground in the most important areas of AI.

If you can afford it get all 3 ;-)

Book 4 is supposed to be coming out this very month.

Yep. Steve Rabin told me a few weeks ago that it was going to the printer and would be out just in time to airlift copies to the booth at GDC. That way I will actually get to touch one before my 2 free copies show up at my house. :)