with pg's onlisp, you don't need any other source.

Relevant excerpt from the introduction

  There are very few good references or tutorials on macro
  construction. Paul Graham's On Lisp[ON-LISP] is one of the
  exceptions. Every word of On Lisp is required reading for anyone
  interested in macros. On Lisp and Graham's other writings were the
  most important inspirations for the creation of the book you are
  reading now. Thanks to Paul Graham and other lisp writers, the power
  that macros provide programmers is widely discussed, yet is
  unfortunately still widely misunderstood. Despite the wisdom regarding
  macro programming that can be gleaned from a simple perusal of On
  Lisp, few programmers make the connection between the macro and their
  real-life programming problems. While On Lisp will show you the
  different types of macros, this book will show you how to use them.

Having read about half of On Lisp, I think that's a fair claim. I am very glad to be reading it, it is a wonderful book, and thanks to it I know what a macro is and what it can do, but haven't really come away with a good feel for when to use them myself in my own code. (It may be that the logic of my code is too simple to require them.) Whether Lambda Over Let lives up to its claim of showing how to use them, I don't know. Definitely going to take a look.