Moving on to actual AI
Once you're done with the introduction to LISP, move on to actual Artificial Intelligence. Just get any book really. Just for an introduction. See what the fields are and how the whole thing flows together. I won't suggest any particular book simply because I've seen a lot of them and they were all basically the same.
AI is a vaste subject. A whole discipline is more like it. Don't get overwhelmed by the hugeness. You'll probably only be working on a very small subset of it.
Don't decide on the field you wish to work in just yet. First you have to get a feel of all of them (hopefully) before you pick the one you can be best at!
The next post will be about Prolog! The easiest language I've yet seen. And I have seen a lot :) We'll start artificial intelligence programming in Prolog!