This book was written before craft beer and the Internet had become integral parts of popular culture in America, an important fact to bear in mind. Some of the information is outdated, but given the resources available at the time, this must have been a landmark volume. It helps provide a framework for describing beer, and though the state of the art has advanced considerably since publication, the book retains its value as a reminder of where we came from and how we got where we are today. I'm reminded of the old Bill James Baseball Abstracts, which seem quaint now but which were groundbreaking when published, spawning more ambitious and refined works and enhancing our knowledge and understanding of what we now take for granted as obvious because of the solid foundation they provided.
This is a tough one to rate and comment on. It is a definite classic and a first of its kind but based on many other attributes it ought score lower. Nonetheless, I ordered myself a used copy via abebooks as it is a major classic in beer books.