During a discussion of the Creative Class concept, Jon Udell notes in passing that author interview and other book summaries (MetaBook) can reduce readership of the underlying book. I Commented...
I think most (Non-Fiction) books are too Fat (Fat Book). Perhaps the future is a Thin Book in print with HyperBook for detail?
Also, is the goal of Writing A Book only/mainly to have people read the book, or to spread the ideas within the book? Perhaps the book is just an anchor for a looser Conversation (Social Object).
Of course, this doesn't cover the issue of how you get paid for that Conversation (Business Models For Information). But people like Dave Winer and Hugh MacLeod always point out that they Make Money because of their WebLog-s, but not from their blogs. Similarly, Richard Florida makes some nice change from his speaking fees, etc. (And lots of books get bought but not read...).