Doom fiends can start salivating. Thanks to The Doom Hacker's Guide (MIS: Press, $21.95) everyone from novices to fanatics can now edit and customize the labyrinthine worlds of Doom and Doom II. The game sends players on perilous interplanetary missions in a duel to the death against otherworldly forces. The Guide includes a CD-ROM with utilities to create add-on levels with torture chambers and secret passages and to edit in new graphics and sounds. With the help of this book, if you can boot up a computer you can make fodder of Barney or the Energizer Bunny. Or you can substitute the Baron of Hell's cry with, say, the bleating of your neighbor's car alarm. For those who crave virtual carnage, author Hank Leukart offers the opportunity to personalize the horrors of Doom and test the limits of your macabre imagination.