I had to chuckle a number of times in reading this, reflecting on various psychiatrists that I encountered in my years of “metaphysical studies”, as some of them seemed to have only gotten into that line of work for the drugs, and were frequently in possession of a wide array of psychoactive substances in their traveling kits. Obviously, if one is studying the mind, and subjective states of the mind, it can be argued that one can't really understand the subject without subjecting oneself to the chemicals which create “interesting” states … this goes all the way back to Freud's cocaine use. This is most excessively illustrated here in one section where Siegel is “researching” the conditions that one subject was in during a multi-day stand-off where he shot his sister, watched his infant nephew die of dehydration, shot up the train car they were traveling in, and did a vast lot of coke … which Siegel attempts to match, line for line!
While that is, perhaps, the most extreme of the cases outlined in the book, the dozen he discusses are all pretty bizarre, from the folks who are convinced there are tiny black bugs under their skin (and worms, and other stuff), which they gouge, scrape, burn, etc. to get rid of, to a guy who decides that he is God, but who is frustrated that the Doctor (who had been a stage magician in his youth) is able to produce more dramatic “miracles” than he can. In between, he interviews “Hitler's brain” (an Eliza-like computer program that a neo-Nazi tech wiz had obsessively developed with all the sayings and writings that he could amass from the mad dictator … works with a satellite scientist who had, largely based on a very strange movie, become convinced that a vast conspiracy (and dwarfs) were out to get him … dissuades an old lady from her conviction that nanobots were installed in her teeth by her dentist, causing the title's “whispers” … looks at the situation of a ballerina/hostess whose increasing cocaine use leads her to kill the object of her desires … visions of bugs, and midgets, and assorted other drug-induced critters that leads one man to suicide, and another to killing his girlfriend's kid … a chess prodigy who had “snapped” in Viet Nam, and was living out a progressively more macabre war game around him … a gal who killed her daughter while in the midst of a religious fantasy fueled by a combination of drugs and preachy TV … and a big-time drug dealer who was convinced that he was being stalked by (again) dwarfs.
All these are little trips down the rabbit hole … from the full-on replicating of the train siege to the Hunter S. Thompson like “playing along with” the dealer's dwarf hunts, Siegel is himself caught up in each of these stories, to the extent that one has to wonder how “real” these tales are, and how “fictionalized” they may have become in the telling here. He is the author of a couple of other books (described as “highly regarded”), so I'm assuming that these are fairly close to reality, as strange (and sometimes implausible) they appear to be.
Whispers does appear to still be in print, so you might be able to find it in your local book vendor's psychology section, but it's also out there in the new/used channels for under a quarter for either the hardcover or paperback editions. It's an unsettling, but fascinating read … if the subject matter is of interest to you, it's certainly worth picking up!