In a twist that the author certainly did not intend to happen, his description of books as an ad-free medium led me to think of a model where out of copyright books are printed with in-page ads and distributed for free. Would that work? :)
Once upon a time, ads in books were extremely common. However, writers hated this, and many of them forcefully opposed the practice during contract negotiations.
One publishing house made the mistake of violating a contract provision against ads by putting a cigarette ad in one of Harlan Ellison's books. Harlan responded in his own inimitable way, as described in the "DID HARLAN REALLY MAIL A DEAD GOPHER TO AN EDITOR?" section of http://harlanellison.com/text/newsfaq.txt .
I've actually seen books with ads before, it is not a new concept. Those were rather old books, too (pre-internet). Only very few ads, though, maybe three pages in the whole book.
Filling covers of the books with ads is very common (I can find them in many books printed in the last 100 years, mostly textbooks, technical manuals and paperbacks, of course), but I haven't seen ads anywhere else, yet.
Lots of paperbacks have ads in the last few pages (other books by the same publisher, order forms, sample chapters for the next book in the series, what have you). The difference is that these ads are after the main portion of the text, not marbled into the text itself.
Anyway, reading a book requires a completely different mindset from reading a magazine/ watching TV/ browsing the web. So I guess that's why ads "work" in one medium and not the other.
