KNOWING WHERE TO LOOK, THE ULTIMATE GUIDE TO RESEARCH by Lois Horowitz (Writer's Digest, $16.95). So, you want to know Napoleon's shirt size? Never mind why, the world is full of questions needing answers, and the title of librarian-researcher Lois Horowitz's book says it all. There have been books, of course, that are primarily lists of available reference sources, and while Horowitz does, indeed, run over this familiar ground, too, she goes considerably deeper--into the black art of "how" to go about a research project: getting started, formulating a game plan, and avoiding those treacherous, dead-end pitfalls where you end up with ink-stained fingers, eyestrain but little usable information. A very readable "how to" book that also explores the new research kids on the block--computer data banks and microfilm.