Jackie French's Guide to Companion Planting in Australia and New Zealand. Revised and expanded 2nd Edition.
A good garden looks after itself. Pests? Repel them, trap-crop them, mystify them, and let predators eat them. Weeds? Outgrow them with natural 'herbicides'. Fertility? Let it accumulate naturally with nitrogen fixing and deep rooted plants, and with garden debris and leaves that decay into rich soil. these are the principles that companion planting is based on.