How big is the book market?

This is a deceptively tricky question. Sales numbers are almost impossible to come by. For a publisher, revealing an author’s sales is almost tantamount to revealing their income, so the one source which would really know is constrained from making any revelations. The Association of American Publishers will periodically issue authoritative numbers (generally in dollars), but these numbers represent sales make by those of their members who went to the trouble of reporting to them — and not all publishers are members of AAP, though most members do report. Self-publishing data are so disparate as to be effectively non-existent. Amazon, the single biggest retailer of books, doesn’t provide numbers on any consistent basis. Even when they do, caution needs to be exercised: Amy Chan in her post I Spent $44,000 Launching My Book. Three of Those Dollars Worked, confides “Amazon counts 3 books bought separately as 3 sales toward your sales ranking. But 30 books ordered in one transaction…