What begins as an examination of the best devices for safeguarding possessions--door and window locks, burglar and fire alarms, safes and bicycle chains--quickly proceeds to more serious stuff: telephone ""black boxes"" with taped police messages, guard dogs, motion sensors, letter-bomb detectors, even armored limousines. Sloane sees crooks--or worse--in every corner, and his alarmist advice is aimed at vulnerable house owners with more money than sense. ""For as little as $120 you can turn one room into a fortress haven against invasion of your home by psychopathic types. Here's how to create this bastion of safety."" Do-it-yourself instructions follow. Consumer's Reports lists the same kind of evaluative information without the folderol.