As the subtitle of her book attests, the primary theme of Carol Deppe's book is finding ways to grow food that will work even when times are tough.  If you can't afford store-bought groceries, break your leg and can't spend every minute in the garden, and have to deal with crazy weather, would you still be bringing in a harvest?  Carol Deppe would.

What's her secret?  Mark would sum it up in one word --- backups.  Deppe goes into more depth, recommending diverse plantings of multiple varieties and types of crops, no single main crop, succession planting, using short-season varieties to work around erratic weather, and including animals in your homestead.  Due to climate change, she recommends not counting on crops that are on the edge of their hardiness range in your area, and instead says you should focus on crops that are being grown commercially by your neighbors since these tend to be dependable.