You might find "Genetic Programming: an Introduction" a better read.   
Also there are two free books with a short discussion of ADFs:

A Field Guide to GP:
My book:


On Mar 6, 2010, at 8:31 AM, Magnus Johansson wrote:

> Hello everybody,
> I've come to the stage where I feel I really need to improve my  
> knowledge about the ADF-functionality. The only information I've  
> found online is to brief. I'd like to read a more throughly  
> "explanation".
> Does anyone have any suggestions for a good online explanation or is  
> the best way to read Kozas book directly? ( Genetic Programming II:  
> Automatic Discovery of Reusable Programs ).
> Best Regards
> Magnus Johansson