how to grow a substantial percentage of my family's diet in my back
yard.

This is very possible, as long as you don't include grains, dairy products, and
oils.

Hardly ever mentioned in books, though, is the most time-consuming part of
all--harvesting, processing (culling, washing, chopping, etc.) and preserving
your harvest.

Jeavons' Grow More Vegetables is excellent, but his yield calculations don't
seem to take into account the inevitable bumps along the way--poor weather,
insects, etc.

There's always something.