How good is "Lisp in Small Pieces"?
It is very good in that it contains a wealth of information on all aspects of implementing a lisp interpreter/compiler. It is just a little bit baroque in style, but I suspect this is because it has been translated from French to English. Overall, great book.
( My copy is falling apart. I heard some rumours there was going to be a new edition but I can't find any supporting evidence online.)