THE CAT WHO WALKS THROUGH WALLS by Robert A. Heinlein (Putnam's: $17.95). This is a book that will neither particularly disappoint nor surprise those readers familiar with Robert Heinlein's style. It is told with an excess of that juvenile flippancy which runs through most (though not all) of Heinlein's science fiction. Col. Colin Campbell, the first-person narrator, never ceases his efforts to be cute, thus explaining the otherwise inexplicable subtitle of this volume, "A Comedy of Manners." Unrelenting flippancy can be wearing, even coming from the cynical persona of hard-boiled detective novels, but in these latter books the manner is often ameliorated by an engrossing plot. Not so in "The Cat Who Walks Through Walls." The book opens well enough: "We need you to kill a man," says a mysterious stranger to Col. Campbell. The colonel shakes his head and responds, "I'm not an assassin. Killing is more of a hobby with me." Unfortunately, these are the two best lines in the book that progresesively deteriorates. This may have been an attempt at parodying the conventions of science fiction: time travel, parallel universes, sexual coyness, macho hero, the particular man needed to do a particular job at a particular time, a title irrelevant to the story. My suspicion of humorous intent, however, derives only from the subtitle, not from any evidence in the story. This is not Heinlein's best.