Gardening When It Counts by Steve Solomon is about how to grow a sustenance garden under less-than-ideal conditions, for example if you are not able to irrigate your crops.  He rates crops on how easy they are to grow, and tells you how to be successful with each kind.  There is information about how to start a new garden or restart an old one, how to work with only hand tools (no gas/electricity), what to look for or look out for when buying plants and seeds, how to water or grow (mostly) without watering, how to make good compost, and what to do about many diseases and pests.  His focus is on self-sufficient gardening for the coming hard times - a compelling message!