Reflections on and By Marshall McLuhan . It's perfect for folks like me, who haven't actually read the man's scholarly work, but want to understand what he said and the contexts in which he said it. It's also delightfully designed, juxtaposing bold thoughts with bold graphics to better bring points home. The editor's notes point out that McLuhan was influenced by Harold Innis, whose books Empire and Communications and The Bias of Communication discuss how empires are shaped by their predominant media. Clearly, the internet and Web take space-based media to what is perhaps its extreme.
Readers move through the hierarchy in the way the author intended.
The outline may be quite complex and intricate. The Web changes all that. The Web pounds documents into many small pieces, loosely joined. Now the reader decides the order in which she'll read the pages. The pages lose their context in the hierarchy.