Book excerpt: Gardeners tend to assume that any organic product is automatically safe for humans and beneficial to the environment—and in most cases this is true. The problem, as Jeff Gillman points out in this fascinating, well-researched book, is that it is not always true, and the exceptions to the rule can pose a significant threat to human health. To cite just one example, animal manures in compost can be a source of harmful E. coli contamination if imporperly treated. Gillman's contention is that all gardening products and practices—organic and synthetic—need to be examined on a case-by-case basis to determine both whether they are safe and whether they accomplish the task for which they are intended. Ultimately, Gillman concludes, organic methods are preferable in most situations that gardeners are likely to encounter. After reading this eye-opening book, you will understand why, and why knowledge is the gardener's most important tool.