Investors seeking guidance on the Internet may find some help in After the Gold Rush. The book is published by Innosight, a Massachusetts consultancy associated with the Harvard Business School Press and Harvard Business School's Prof Clayton M. Christensen. Prof Christensen and his colleagues studied a variety of Internet efforts, analysing what worked and what didn't. Though addressed to entrepreneurs, the study provides a framework of questions that investors should ask about companies attempting to use the Internet as part of a business model. The crucial question, the report says, is this: "Does the new business enable a larger population of less-skilled or less-wealthy people to do things for themselves that they could not do before?" Innosight's paper was commissioned by Internet consultancy Concrete Inc (www.concrete media.com). The book analyses Internet portals, real estate, insurance and travel sites, online textbook sales and a variety of other businesses. Copies are available at www.innosight.com.