As its title indicates, Mac OS 9: The Missing Manual touts itself as the guide that should have come with your copy of Apple"s operating system. It certainly makes a strong case for that claim, as author David Pogue offers a wealth of information from the basics to some of OS 9"s more esoteric functions. The book is strongest in its detailed information on operating system components like the Apple menu and using OS 9"s speech-recognition features. Pogue"s explanations of standard, custom, and clean installations of OS 9 are similarly helpful, as is the partial list of the OS"s compatibility problems. The troubleshooting guide isn"t exhaustive, but the problems it does explore are handled in depth. Unfortunately, Pogue refers too often to the pre-Mac and -Windows days when you had to type out a filename and multitasking hadn"t yet become part of the computer vocabulary. It"s not likely that many users today will be upgrading from a 286 DOS machine (remember those?) to an iMac. Pogue is better at explaining some of the subtle differences between Microsoft Windows and iMac conventions. Nonetheless, any Mac OS 9 user will find lots of useful information in The Missing Manual. --John Frederick Moore