Common Lisp: The Untold Story
What has never been clear to me about Lisp is how these implementations differ.  The syntax is so simple it doesn't seem to be that, so that would leave builtins and libraries.  Surely builtins can be emulated and libraries can be ported.So why doesn't there exist some macro (Lispers always brag about them) that could transmogrify code written for one set of builtins and libraries to another?