On the Web, what matters is what you have to offer, and how well you offer it. Books can be ordered, paid for, and delivery status checked online. Heavy discounts and contests are constantly offered to entice surfers to purchase online. A search engine allows you to easily find a book you're interested in. And when you do find a particular book, it shows you the other books people who picked up the title also bought.
Readers can add their reviews and rate books they have read for interactivity.
When a surfer makes a purchase online, he's added to a mailing list that informs him of new offers. Some websites precariously lie between stages - neither here nor there. The more visionary companies start the life cycle directly from stage three. This is either because they've understood the Net, or learnt from other's mistakes. Deciding to launch a website directly in the third stage involves commitment from the management and a bigger budget, but these costs easily override the time and effort that are wasted into the first two stages.