Let Over Lambda (ISBN 978-1-4357-1275-1, 376+iv pp.) is one of the most hardcore computer programming books out there. Starting with the fundamentals, it describes the most advanced features of the most advanced language: COMMON LISP. The point of this book is to expose you to ideas that you might otherwise never be exposed to. This book is about macros, that is programs that write programs. Macros are what make lisp the greatest programming language in the world. When used properly, macros enable amazing feats of abstraction, programmer productivity, and code efficiency and security that are unheard of elsewhere. Macros let you do things you simply cannot do in other languages.
In learning to write Scheme macros, I have noticed that it is easy to find both trivial examples and extraordinarily complex examples, but there seem to be no intermediate ones. I have discovered a few tricks in writing macros and perhaps some people will find them helpful.