Let Over Lambda is one of the most hardcore computer programming books out there.
This book is about pushing t.
If you are looking for a dry coding manual that re-hashes common-sense techniques in whatever langue du jour, this book is not for you.
Only the top percentile of programmers use lisp and if you can understand this book you are in the top percentile of lisp programmers.
Starting with the fundamentals, it describes the most advanced features of the most advanced language: Common Lisp.
Let Over Lambda is one of the most hardcore computer programming books out there