More than a decade after her groundbreaking study, The Second Self (1984), MIT psychologist Turkle returns to the subject of human views of and relationships with computers (and through computers, with each other and themselves). This readable if somewhat diffuse study draws again on a wide range of interviews with computer usersfrom children and graduate students to professional programmers and MIT physicists. Turkle explores what the rapid growth of the Internet has meant to our society. She's especially interested in ``MUDs'' and ``MOOs''text- based virtual environments, accessed through the Net, where users can adopt online personas and interact with others, sometimes becoming so involved in this role-playing that it seems ``more real'' to them than their lives outside the screen. Turkle makes a convincing case that some MUDders get an effective form of therapy in these virtual worlds, that the freedom to adopt different characters (even different genders and species) allows them to explore parts of themselves that remain buried in the real world. But she unfortunately downplays the escapism and withdrawal from reality many MUDders display. She also offers a very interesting analysis of the transformation over 15 years of attitudes toward artificial intelligence, from repulsion to acceptance and even eager anticipation, arguing that the fledgling realm of ``artificial life''creating lifelike ``organisms'' in computerized environmentsrepresents the more pressing challenge to our cultural sensibilities today. Though many of Turkle's insights are nothing new, she makes a vital contribution to the study of Internet culture with her heavy reliance on the experience of actual users (often quoted at length). With that concrete grounding, her study stands out among the flock of recent Internet critiquesan informed and informative look at our ever-changing relationships with machines.