Gaia’s Garden is an excellent, reader friendly way to become introduced to permaculture ideas. It was my first book and continues to be my favorite.
Permaculture is based on a great deal of perennial plants vs annual plants. By not harvesting the plants, only parts of the plants, placing a much smaller burden on soil. It also includes a wide range of support planting allowing the different plants to provide various nutrients to the soil.
The other nice thing about permaculture gardens is they often do not look like traditional gardens. They also require much less work each year to maintain, with each year getting easier. It also introduces a wide range of plants that are edible, but not common. This provides for a more varied diet and makes the garden less of a target. In fact many permaculture set ups look much like a bunch plants growing everywhere.
I was introduced to this by a woman named Christie Faith. She has a garden, aquaponics, chickens, ducks and a bee hive in a rather small back yard in downtown Colorado Springs, Colorado. Her website it http://www.righttothrive.org if you are interested in her blog.