Sullivan mentions that hydroponics--soilless culture, or 'raising plants in a liquid that provides water and nutrients--""might be part of the solution"" to the world food crisis; and if the tomatoes he describes--abundant, meaty, juicy, superb in flavor and extra nutritious--become widely available, that alone would justify the practice. But though he lists advantages and disadvantages as well as sketching the history of this kind of farming, he leaves you without a clue as to its degree of promise or practicality. Scientific background is minimal--only in a short final chapter on ""mixing your own nutrients"" do we learn what these minerals are and even then their special functions are but vaguely defined. The rest of the book offers tips for growing common houseplants hydroponically and for growing vegetables from seed--a hobby that can become forbiddingly expensive, but could prove an interesting experiment on a smaller scale. A novel how-to, then, but short on why's and whither's.