I have been a stamp collector for over 40 years, a postal historian and a philatelist for about 15 of those years and a specialist collector of revenue stamps and documents for the last 5 years. I've been a member of some the most friendly and well-run groups you could ever imagine - the State Revenue Society and the American Philatelic Society are both examples of best practice - and I even flirted briefly with philatelic exhibiting. Despite having served such a lengthy apprenticeship I still don't have an answer to a really basic question: Why are postage stamps catalogued, collected and researched with so much more energy and enthusiasm than revenue stamps? There are many countries where there doesn't seem to be a reliable and up-to-date catalogue of revenue stamps - certainly not one accessible to a virtual monoglot such as myself. I think it comes down to what I call "critical mass." Without enough revenue stamp collectors it is hard for dealers to establish a viable business, but without dealers generating catalogues and generally raising the profile of this branch of the hobby I suspect that prospective revenue stamp collectors tend to wander off into the sunset searching for easier pickings. Thanks to the outstanding work of members of the State Revenue Society the United States of America is an honourable exception to this problem. The recently published "State Revenue Catalog," edited by Dave Wrisley, is a masterpiece of philatelic literature. Many collectors specialise in the revenue stamps of a single USA state or on stamps issued for one particular product or service. I prefer the topical approach where my collection is based on obtaining an example of every different tax that was levied. This small study is intended to bring to the attention of the wider collecting public the sheer diversity of state revenue stamps issued in the USA. The categories presented within the book are based on those used in the "State Revenue Catalog."