I would definitely recommend this rather long, quite smart article by Andy Beckett in the Guardian all about the current, potentially troubled state on smart non-fiction, in the UK and the US. (Link came from BookNinja.)
It reminded me of a book I read some time ago, that clearly influenced my thinking:
The literary agent Peter Straus, previously a publisher at Picador, is also worried: "It is more and more difficult to place good books. Retail's changed. Advances have come down in the last two years. So many books haven't sold. There are too many books published. The harsh realities of the market will impinge on certain writers, certain publishers, certain agents."
In his 2000 polemical history The Business of Books: How International Conglomerates Took Over Publishing and Changed the Way We Read, the veteran American publisher André Schiffrin calls this process "market censorship". But one person's market censorship is another person's market realism.
Market censorship - must remember that and give credit where credit is due.
Enjoy the article, folks!