While it seems problematic to come up with a top N set of best sellers in Economics, there is an extensive body of scholarship one can draw on regarding the history and economics of publishing that should allow one to put Henry George in some sort of perspective as a best selling economics author. Indeed there is a scholarly association, the Society for the History of Authorship, readership, and publishing (SHARP) -- or something like that-- that delves into such issues for publishing broadly. One consideration is whether publishers, such as George's maintained records of print runs as well as book prices. Of course there are complications such as George's works going through multiple editions with multiple publishers. But looking at evidence on print runs and numbers of printings for some of George's major works with some of his leading publishers should at least provide perspective. One can then compare the magnitudes with what one can glean on other likely leading economics sellers. THere may be some evidence out there on numbers of copies sold of Samuelson's textbook in various editions as well as say Mankiw. My recollection is that Keynes intended his General Theory believe it or not to have a wide readership and tried to get it priced by his publisher accordingly. It should stand to reason that most leading authors of economics texts would be aware of how their books are selling and there should be some indications in their biographical details of the magnitude of the income flows involved. I don't claim there is an easy answer to the issue of establishing comparable best sellers to progress and poverty but it is an issue one should at least be able to address with due archival digging. If Victorian literature scholars can take up this issue for say Dickens and George Eliot, which I am almost sure they have, I dont' see why historians of economics shouldn't be able to pursue the same for writers such as Henry George. David Mitch