About all this Lisp fuzz
blue1: Which lisp are you talking about? For example, Common Lisp and Scheme are both languages of the lisp family, but they are rather different.The PG books are about Common Lisp. CL is defined in a very good ANSI standard. Where implementations of CL really diverge is in the areas which  are not covered by the standard, e.g. networking. Not that it is an enormous problem in practice: there are good portable libraries around ("portable" means that they work on different CL implementations).edit: thinking about it, if you are using Peter Seibel's lisp in a box, then it's CL that you are playing with