It's not exactly an easy read -- whenever I recommend it to someone I also warn them that it contains the most passive sentence in the history of the English language: "Information obtained by a member of group A about the compiler resulting from the further modification of it after about 10 years made it clear that at that later stage the original powerful structure was still visible, but made entirely ineffective by amorphous additions of many different kinds."

But the content more than makes up for the style!