Berkeley) and Peter Norvig (Director of Research at Google) is the standard introductory textbook to AI theory and application at the undergraduate level.
It's friendly in the sense that it requires less mathematical maturity, and assumes less mathematical background. It does have a very comprehensive and broad survey of the entire field, which is good in that it gives the student a sense of the entire field, but bad in that there is much less depth in any single area.
If you are looking for a single good introductory textbook to get started into research, there are probably better alternatives (such as Pattern Recognition and Machine Learning, which I also reviewed). But if you are looking for a single good introductory textbook to understand the field better, and not necessarily to prepare to do original research, this is probably a great book to start with and I recommend it highly.
A word of caution of the term "artificial intelligence" though. Much of the algorithms and techniques referred to in this text are probably more accurately described as machine learning or statistical pattern recognition algorithms. If you are looking for a book on artificial general intelligence, you will be disappointed.