It may not help or be relevant - but my chickens only eat about 40p's worth of food a week and get me 14 eggs a week - which goes a long way towards my food bill.
Also if you can access a market - you can get the friut/veg a little past their best - but as long as you cook that day (and maybe freeze) it's OK.
Changing the proportions of food on your plate helps too. Currently meat/fish is often 1/3rd to 1/2 of your food. It can drop to about 1/6 (or 1/4) without any lasting effects, carbohydrate can be increased along with veg, eg add a slice of bread and butter, or mop up the gravey with a slice of bread.
Scrambled egg with half a tin of tuna in can be served with veg as a lovely meal (5-10 min)
Lots of pasta with Tuna & cheese, or ham & Cheese, or tomato salsa (15-20 min)
Toad in the hole with mash, carrot & onion gravey (my littles only eat a couple of cocktail sauages each) (30 min)
Homemade soup - the flavours are endless (and great for using veg past it's best) (prep in the am and slow cook or make a batch at weekend and freeze- 2hrs plus ) or if you are in a hurry a frozen bag of casserole mix, a stock cube, some herbs (or stuffing mix) boil for 20 mins and liquidise.
Sweet potatoe pie or cheese & potatoe pie with beans goes down well here too (20-30 mins depends how small you cut the potatoes)
I think my homemade bread is cheaper than bought - but I do eat a bit more of it
Good luck finding a book