If one has serious interest in expert level Common Lisp code there is the Norvig's masterpiece Paradigms of Artificial Intelligence Programming (PAIP) which is

If one has serious interest in expert level Common Lisp code there is the Norvig's masterpiece Paradigms of Artificial Intelligence Programming (PAIP) which is available form Amazon or torrents. There is also the Common Lisp code from AIMA second edition. PAIP and AIMA for CL is the same as SICP and old classic HtDP for Scheme. After mastering these one might consider oneself a programmer.)