Publishers Weekly reports that book sales fell 1.8% in 2009 to US$23.9 billion:

Trade sales were nearly flat in the year, slipping 0.1%, to $8.1 billion as adult hardcover sales rose 6.9% and children’s paperback sales increased 2.2%. Sales of trade paperback declined 5.2% and children’s hardcover sales fell 5.0%. The star of the year, of course, was the e-book category that AAP estimates grew 176.6%, to $313.2 million.

In other categories, mass market paperback revenue fell 4.0%, to $1.0 billion, and book club and mail order sales dropped 2.0%. Sales in the religious book category are estimated to have declined 9.0%, to $658.7 million. Sales of spokenword audio were reported down 12.9%.

The PW article doesn’t disclose other data that would help clarify the relevance of these numbers, such as whether shipments rose or fell, nor did it break out which genres outperformed or underperformed.

Nonetheless, year-on-year declines do not bode well for the sector.