Not much, apparently. I’m still trying to get my arms around the enormity of this information (thanks to Bovril):
This is a chart of sales by Amazon.com of Jerome Corsi’s book, Where’s the Birth Certificate? The book was reported as the #1 non-fiction bestseller at Amazon.com in April, and according to the chart from NovelRank.com, the book pre-sold a total of only 837 copies that month! The book was released in May where it sold a whopping 2,232 copies on Amazon, making it a national bestseller (perhaps with the help of bulk orders from other retailers as reported by the NY Times). Sales ranking at Barnes & Noble lagged far behind those at Amazon.
Perhaps this explains why used copies of WTBC? were so scarce. I finally got my used copy yesterday. I never thought it would be a collector’s item.