Publishers select certain manuscripts or content from a sea of possible candidates. Texts are then made ubiquitous, though accessible only as commodities. The web makes a billion texts accessible, but hardly detectable. The network, in other words, requires a degree of hierarchy, selection, and topographic organization. The network is not inimical to hierarchy of a kind.
Web pages have home pages.
The net has portals, etc. But what we find in the book is more than just information. Written content on the web is somewhere between email and the book, but mostly closer to email. The economics of publishing make this necessary. There may be more and better information available on the web, but the function of the book is guaranteed for a long time to come by virtue of being a kind of elaborate portal to a subject.