Bob Flowerdew's Complete Book of Companion Gardening by Bob Flowerdew
Covering both theory and practice, this is a guide to the technique of using the beneficial relationships of plants growing in close proximity to one another. Some plants are useful because they shade smaller ones; some accumulate minerals that benefit others; some attract pests and can be used as sacrificial plants alongside a more valuable crop; others just seem to do better with certain plants nearby. The book includes ideas and lists of plants suitable for certain positions in the garden.