I highly recommend "How to Grow More Vegetables: Than You Ever Thought Possible on Less Land Than You Can Imagine" by John Jeavons.
Every year, my garden produces an ever increasing portion of the food for my household and this year it has expanded to provide a significant amount of food for a small flock of chickens. Important things that aid my productivity and reduce the time it takes are a heavy mulch to minimize weeds, improve soil fertility and reduce water consumption as wel as drip irrigation on timers.
There are plenty of people using sustainable techniques to produce more food than they can eat if you look around on the internet.