There is a recipe book published by Family Circle called 'Commonsense Cooking' - you can pick it up from newsagents for around $15. Mum bought me one when I was a teenager and it is the best cook book - has all the basics and honestly, everything in there is virtually fool proof. Haven't had a single recipe from that cookbook turn out badly.
I'm going to second how good this cookbook is!
We have book sellers that come in to work, and I swear nearly everyone must have ordered this book off him, even if theres none in the book boxes/order form to buy people will just jot it down on the sheet anyway with a 'please please??' attached. So I'm guessing its amazing!
(I haven't got it, my fave cookbooks are the Frankie Afternoon Tea cookbook, and AWW 1000 Best Ever Recipes)
I'll add to the list with must know:
basic cookie dough (so you can add whatever you like to it!)
And in my house: