Miessler, a gardener and permaculture designer, provides fellow horticulturalists with a guide to the mostly hidden but essential world of soil in her valuable book. She begins with a general breakdown of soil's components: 45% minerals, 20%--30% air, 20%--30% water, and 5%--10% organic matter. Then, using a house metaphor, the book explores in detail the last of these "building blocks"--organic matter. All healthy soil, she writes, needs a good "roof," that is, mulch and cover crop. The house's "walls" comprise the microbes, fungi, protozoa, and other organisms that live in the soil. "In your quest for good soil," Miessler notes, "the most important thing you can do is always this: add organic matter." Completing the house metaphor, the book culminates in a section called "Feed the Inhabitants," highlighting ways to nourish plants through soil rich in sugars (through photosynthesis) and minerals (via manure and other sources of nitrogen, an essential nutrient for plants). Miessler's exploration goes to a level of organic chemistry that may not suit casual dabblers, but the richness of knowledge in her erudite work will excite any serious backyard or commercial organic gardener. (Feb.)